CN105523195A - Material selection method of aircraft structure based on series material property indexes - Google Patents
Material selection method of aircraft structure based on series material property indexes Download PDFInfo
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Abstract
The invention discloses a material selection method of an aircraft structure based on series material property indexes. The material selection method comprises the following steps of setting material selection structure targets according to the design requirements of the aircraft structure; setting structure functions and design demands; setting structure importance and maintenance cost; setting structure stress situation and functional requirements; setting a structural design criterion according to the structure importance and the maintenance cost, preliminarily setting the scope of alternative materials according to the design requirements of the aircraft structure, and further setting the scope of the alternative materials according to the structure stress situation and the functional requirements; sequencing materials according to the bearing characteristics of the structure, the structural design criterion and the scope of the alternative materials through comparison of different materials on the specific stiffness, the specific strength, the specific fatigue strength, the fatigue strength ratio, the specific tenacity, the static obdurability ratio, the weariness obdurability ratio of different materials; performing material selection; and judging whether the selected materials meet the demands for structural design, manufacturing and use or not. According to the material selection method disclosed by the invention, high service use safety of the aircraft structure can be guaranteed, the weight of the aircraft structure can be alleviated, the flight properties can be improved, and the use cost can be reduced.
Description
Technical field
The invention belongs to field of airplane structure, particularly a kind of aircaft configuration selection method based on series material performance figure.
Background technology
Aircraft, as a kind of air vehicle, has the advantages that after structural damage, accident rate is high, operating cost is high, and therefore, aircaft configuration has clear and definite requirement to choosing of its material: one is requirement of strength, to ensure the military service safety of aircaft configuration; Two is weight demands, alleviates structural weight as much as possible, make flight cost minimum under the prerequisite ensureing structural strength.
Along with improving constantly of aeroplane performance index, in order to ensure the safety of aircaft configuration, aeroplane structure design thought experienced by the Static Strength Design stage, static strength and rigidity Design stage, intensity, rigidity, structural safety Life Design stage and intensity, rigidity, damage tolerance and durability Design stage.The static strength of structural static strength design philosophy claimed structure meets the requirement of regulation; The distortion of structural Rigidity Design thought claimed structure meets the requirement of regulation; The requirement meeting regulation fatigue life of structural safety Life Design thought claimed structure; The economical life of durability design of structure thought claimed structure meets the requirement of regulation; Structural damage tolerance design thought requires that structural crack expands the requirement that the life-span meets regulation under the condition that there is initial defect.Present stage, China's aeroplane structure design uses the structure integrity design philosophy including structural strength, rigidity, safe life, durability and damage tolerance etc.: first, aircaft configuration all will meet static strength and rigidity Design requirement; Secondly, according to the task feature at position concrete in aircaft configuration, the designing requirement that they are different is selected.Such as, the crucial load-carrying construction of aircraft generally will meet damage tolerance and durability Design requirement, stress sensitivity ad hoc structure that is high or not easily maintenance and inspection generally will meet safe-life design requirement, and most of load-carrying construction of aircraft generally will meet the life requirements etc. that can carry out economic repair.
Above-mentioned structure design thought all has the material property parameter of its correspondence, and such as, structural static strength designs the correspondence tensile strength of material, which characterizes the ability of the quiet tensile load of material repels; Structural Rigidity Design the is corresponding modulus of elasticity of material, which characterizes the ability of material repels distortion; The damage tolerance design of structure the is corresponding fracture ductility of material, which characterizes the ability of material repels fracture by fatigue; The durability Design of structure and safe-life design the are corresponding fatigue limit etc. of material, which characterizes the ability of material repels fatigue cracking.Above-mentioned material property parameter only reflects the mechanical characteristics of material, also needs to consider the density of material if be applied in the selection of aircaft configuration, namely needs to consider the mechanical property levels of material under unit weight.For this reason, people propose the concept of material strength-to-density ratio and stiffness-to-density ratio in engineering practice.Strength-to-density ratio is strength-to-weight ratio again, is the tensile strength of material and the ratio of density of material; Stiffness-to-density ratio is named again than modulus or than modulus of elasticity, is the modulus of elasticity of material and the ratio of density of material.The strength-to-density ratio of material is larger, shows that the structure quality of materials used when reaching respective strengths is lighter, and that is the usefulness of material when carrying is higher; The stiffness-to-density ratio of material is larger, shows that the structure quality of materials used when reaching corresponding rigidity is lighter.
But, strength-to-density ratio only reflects the static strength performance of material under unit weight, stiffness-to-density ratio only reflects the rigidity property of material under unit weight, and what in fact most aircaft configuration bore is tired alternate load, and its structure design thought is also not quite similar.Therefore, this patent proposes a kind of selection method of aircaft configuration, on the basis of strength-to-density ratio (also known as material than static strength), stiffness-to-density ratio, propose material than strength at repeated alternation, fatigue ratio, than toughness, quiet tough ratio, tired tough ratio totally 5 material performance indexs, and give the method step carrying out aircaft configuration selection according to 7 material performance indexs.
Summary of the invention
The object of the invention is to overcome in existing product not enough, a kind of aircaft configuration selection method based on series material performance figure is provided.
In order to achieve the above object, the present invention is achieved by the following technical solutions:
A kind of aircaft configuration selection method based on series material performance figure of the present invention, the method comprises the following steps:
1) according to the structure objects of the design requirement determination selection of aircaft configuration;
2) structure function and designing requirement is determined;
3) structure importance and maintenance cost is determined;
4) structure stress situation and functional requirement is determined;
5) determine five kinds of structural design criterions according to structure importance and maintenance cost, according to the design requirement initial setting candidate materials scope of aircaft configuration, set candidate materials scope further according to structure stress situation, functional requirement;
6) carry out material contrast according to the load characteristic of structure, at least one structural design criterion, candidate materials scope and sort;
7) Material selec-tion is carried out;
8) judge whether selected materials meets structure design, manufacture, operating needs, if selected materials meets structure design, manufacture, operating needs, then carry out determining the final selection of structure, if selected materials does not meet structure design, manufacture, operating needs, then re-start Material selec-tion, until selected materials meets structure design, manufacture, operating needs, if re-start Material selec-tion, selected materials still cannot meet structure design, manufacture, operating needs, then the function that restructures and designing requirement.
The structure objects of selection of the present invention is the composition structure forming airframe or the structure that can threaten to flight safety when it lost efficacy.
Structure function of the present invention comprise load, power transmission, maintenance aircraft aerodynamic configuration, form specific local space.
Structure importance of the present invention is the influence degree to flight safety after aircaft configuration lost efficacy.
Structural design criterion of the present invention is take different design criterias for Different factor, and design criteria comprises Static Strength Design criterion, damage tolerance design criterion, durability Design criterion, safe-life design criterion.
Factor of the present invention comprises the structure being not easy to inspection and maintenance in superhigh intensity steel structure in load-carrying construction, the crucial load-carrying construction of aircraft, the angle of economy, aircraft, aircraft, takes Static Strength Design criterion, takes damage tolerance design criterion according to the crucial load-carrying construction of aircraft, takes durability Design criterion according to the angle of economy, takes safe-life design criterion according to the superhigh intensity steel structure in aircraft, take safe-life design criterion according to the structure being not easy to inspection and maintenance in aircraft according to load-carrying construction.
Aircaft configuration of the present invention design requirement comprises load bearing requirements, weight demands, volume requirement, resistance to corrosion requires, fail-safety requires, welding performance, penetrability require, thermal environment requires, electromagnetic wave shielding requires, insulativity requires, cost requirement.
According to penetrability, the present invention requires that initial setting candidate materials scope is in the scope of translucent material, require that initial setting candidate materials scope is in the scope of heat-resisting material according to thermal environment, require that initial setting candidate materials scope is in the scope without electromagnetic shielding material according to electromagnetic wave shielding, according to without design requirement initial setting candidate materials scope in steel, aluminum alloy, titanium alloy, composite material.
Only refer to only by the structure of static load or the structure being subject to cyclic loading that load is large in life cycle management according to Static Strength Design criterion, and the rigidity requirement of structure is low, the rigidity of material can meet structural requirement automatically, carry out contrast sequence according to the ratio static strength of candidate materials, the material more maximum than static strength is optimum;
Only referring to structure according to rigidity Design criterion reaches rigidity Design index, and material can meet static strength requirement automatically, only needs to carry out contrast sequence according to the stiffness-to-density ratio of candidate materials, the material optimum that stiffness-to-density ratio is maximum;
Only referring to structure according to damage tolerance design criterion reaches damage tolerance design index, and material can meet structure at the static strength contained under crackle state and rigidity requirement, carry out contrast sequence according to the ratio toughness of candidate materials, the material more maximum than toughness is optimum;
Only refer to when structure reaches durability Design index according to durability Design criterion, and material therefor meets static strength and rigidity requirement, then carry out contrast sequence according to the ratio strength at repeated alternation of candidate materials, the material mechanical performance more maximum than strength at repeated alternation is optimum;
Only refer to when structure reaches safe-life design index according to safe-life design criterion, and material therefor meets static strength and the rigidity requirement of structure, carry out contrast sequence according to the ratio strength at repeated alternation of candidate materials, the material more maximum than strength at repeated alternation is optimum;
According at least two kinds of design criterias, then according to the ratio of design objective corresponding to each design criteria, contrast sequence to be carried out according to fatigue ratio, quiet tough ratio or tired tough ratio.
Strength-to-density ratio is referred to, namely γ than static strength
σ/ρ, refer to the tensile strength sigma of material
bwith the ratio of density of material ρ, i.e. γ
σ/ρ=σ
b/ ρ, the tensile strength sigma of material
brefer to limit stress during Materials Fracture;
Stiffness-to-density ratio is exactly γ
e/ ρ, refer to the elastic modulus E of material and the ratio of density of material ρ, i.e. γ
e/ ρ=E/ ρ;
Be exactly γ than toughness
k/ ρ, refer to the fracture ductility K of material
iCwith the ratio of density of material ρ, i.e. γ
k/ ρ=K
iC/ ρ
Be exactly γ than strength at repeated alternation
s/ ρ, refer to the fatigue limit S of material
-1with the ratio of density of material ρ, i.e. γ
s/ ρ=S
-1/ ρ, the fatigue limit S of material
-1refer under the constant-amplitude fatigue loading of stress amplitude ratio R=-1, material can bear unlimited cycle of stress and the maximum stress of destruction not occur, and that reflects the level of material repels fatigue cracking or fatigue of material performance;
Fatigue ratio is exactly γ
s/ σ, refer to the fatigue limit S of material
-1with tensile strength sigma
bratio, i.e. γ
s/ σ=S
-1/ σ
b, what what fatigue ratio represented was between durability criterion and Static Strength Design criterion lays particular stress on degree;
Quiet tough ratio is exactly γ
s/ σ, refer to the fracture ductility K of material
iCwith tensile strength sigma
bratio, i.e. γ
k/ σ=K
iC/ σ
b, quiet tough be the degree that lays particular stress between damage tolerance design criterion and Static Strength Design criterion than what represent;
Tired tough ratio is exactly γ
k/s, refer to the fracture ductility K of material
iCwith fatigue limit S
-1ratio, i.e. γ
k/s=K
iC/ S
-1, tired tough be lay particular stress on degree between damage tolerance design criterion and safe-life design criterion or durability criterion than representing.
Beneficial effect of the present invention is as follows: the present invention improves evaluation of material system and reasonably determines that aircaft configuration selection provides Theories and methods support, thus aircraft utilization economy is improved under the prerequisite ensureing flight safety and aircraft technology index, the present invention is on the basis that ensure that aircraft structure strength requirement, carry out rational material selection, not only can ensure the military service safety in utilization of aircaft configuration, and can aero-structure weight be alleviated, improve airworthiness, reduce use cost, the series material performance figure that the present invention proposes, not only can realize the mechanical property contrast between different materials, and can reflect that material lays particular stress on degree in different mechanical properties, examination and the critical for the evaluation of material are quantized, and can apply and other field except aviation field, applied range.
Accompanying drawing explanation
Fig. 1 is schematic flow sheet of the present invention;
Fig. 2 is the performance figure schematic diagram of candidate materials of the present invention.
Detailed description of the invention
Below in conjunction with Figure of description, technical scheme of the present invention is described further:
A kind of aircaft configuration selection method based on series material performance figure of the present invention, the method comprises the following steps:
1) according to the structure objects of the design requirement determination selection of aircaft configuration;
2) structure function and designing requirement is determined;
3) structure importance and maintenance cost is determined;
4) structure stress situation and functional requirement is determined;
5) according to structure importance and maintenance cost determination structural design criterion, according to the design requirement initial setting candidate materials scope of aircaft configuration, candidate materials scope is being set further according to structure stress situation, functional requirement, the factors such as the structure importance determined, structural repair cost are by for determining that the design criteria of structure lays the foundation, and the factors such as the structure stress situation determined and functional requirement provide foundation by for determination candidate materials scope afterwards.
6) carry out material contrast according to the load characteristic of structure, structural design criterion, candidate materials scope and sort;
7) Material selec-tion is carried out; The most forward material of selected and sorted carries out the checking of every structure design demand as first material selection.
8) judge whether selected materials meets structure design, manufacture, operating needs, if selected materials meets structure design, manufacture, operating needs, then carry out determining the final selection of structure, if selected materials does not meet structure design, manufacture, operating needs, then re-start Material selec-tion, until selected materials meets structure design, manufacture, operating needs, thus determine the final selection of structure, if re-start Material selec-tion, selected materials still cannot meet structure design, manufacture, operating needs, then the function that restructures and designing requirement.If the material of checking can not meet design, manufacture and operating needs in step 8, then according to the material sequence in step 7, the material of next order is selected to carry out the checking of step 8, until meet the demands; The situation not having suitable material to meet the demands if occur, then need the design of structure, manufacture or operating needs to relax, or the design that restructures.
Investigation in this step is to liking the aircaft configuration be made up of first material selection, the content investigated comprises mechanical performance index, as static strength, rigidity, fatigue life, durability, damage tolerance level etc., special needs are considered to be positioned at high-altitude when aircraft, and temperature is lower than material mechanical performance index when-50 degrees Celsius; Economic index, as structural materials cost, structure tooling cost, structural maintenance cost, the material supply of goods etc.; Processing difficulty or ease level index, as hardness, welding requirements, cutting ability, smelting technology, Technology for Heating Processing, surface treatment etc., other index, as resistance to corrosion requirement, volume requirement, structural functionality requirement etc.
The structure objects of selection of the present invention is the composition structure forming airframe or the structure that can threaten to flight safety when it lost efficacy.
Structure function of the present invention comprise load, power transmission, maintenance aircraft aerodynamic configuration, form specific local space.
Structure importance of the present invention is the influence degree to flight safety after aircaft configuration lost efficacy.
Structural design criterion of the present invention is take different design criterias for Different factor, and design criteria comprises Static Strength Design criterion, rigidity Design criterion, damage tolerance design criterion, durability Design criterion, safe-life design criterion, safe-life design criterion.
Factor of the present invention comprises load-carrying construction, need avoid the structure producing Aeroelastic Problems maybe can not occur excessive deformation so that affect the structure of aeroplane performance, the crucial load-carrying construction of aircraft, the angle of economy, superhigh intensity steel structure in aircraft, the structure of inspection and maintenance is not easy in aircraft, Static Strength Design criterion is taked according to load-carrying construction, avoid producing the structure that the structure of Aeroelastic Problems maybe can not occur excessive deformation so that affect aeroplane performance as required and take rigidity Design criterion, damage tolerance design criterion taked by crucial load-carrying construction according to aircraft, durability Design criterion is taked according to the angle of economy, safe-life design criterion is taked according to the superhigh intensity steel structure in aircraft, superhigh intensity steel structure comprises alighting gear, safe-life design criterion is taked according to the structure being not easy to inspection and maintenance in aircraft.To the crucial load-carrying construction of aircraft, very high fiduciary level and security level is had in order to ensure it, even if generally consider structure to be designed to exist crackle from the angle of safety also can have enough residual intensities to ensure safety not repairing in used life, namely damage tolerance design criterion is adopted, for some aircaft configurations, though safety problem can not be caused immediately when cracking occurs for it, but the performance of structure function can be had influence on, structural maintenance requirement and life cycle cost etc., if can not repair in time when exceeding certain crack size, uneconomical, generally from the angle of economy, structure is designed to have opposing cracking at the appointed time, corrosion, peel off, wearing and tearing, the ability of Foreign Object Damage etc., namely durability Design criterion is adopted.One is some the superhigh intensity steel structure in aircraft, as alighting gear, this class formation counter stress is concentrated with initial defect very responsive, generally be not designed to damage tolerance structure, and the difficulty of carrying out keeping in repair is comparatively large, is not also designed to durable construction, generally adopts safe-life design criterion to it, careful inspection is carried out, to guarantee to control initial damage after structure machines; Two is the structures for being not easy to inspection and maintenance in aircraft in total life cycle, as some main force support structure of aircraft of being on active service on U.S. army's aircraft carrier, owing to lacking necessary inspection, overhaul condition in life cycle, generally also take safe-life design criterion.Adopting the structure of safe life criterion design when reaching the safe life of regulation, namely it being changed
Aircaft configuration of the present invention design requirement comprises load bearing requirements, weight demands, volume requirement, resistance to corrosion requires, fail-safety requires, welding performance, penetrability require, thermal environment requires, electromagnetic wave shielding requires, insulativity requires, cost requirement.
According to penetrability, the present invention requires that initial setting candidate materials scope is in the scope of translucent material, require that initial setting candidate materials scope is in the scope of heat-resisting material according to thermal environment, require that initial setting candidate materials scope is in the scope without electromagnetic shielding material according to electromagnetic wave shielding, according to without design requirement initial setting candidate materials scope in steel, aluminum alloy, titanium alloy, composite material.Such as, the canopy structure having penetrability to require, can delimit the scope at the translucent material such as organism glass and case hardened glass by candidate materials; There is the engine blade structure of thermal environment requirement, candidate materials can be delimited the scope at heat-resisting material such as steel, titanium alloy, stupaliths; There is the radome structure of electromagnetic wave shielding requirement, candidate materials can be delimited in the scope without electromagnetic shielding material such as carbon fiber composite material and glass fiber compound material.If the structure chosen does not have particular/special requirement, then the candidate materials scope tentatively determined generally selects the main load material of present stage, as steel, aluminum alloy, titanium alloy, composite material etc.
Only refer to only by the structure of static load or the structure being subject to cyclic loading that load is large in life cycle management according to Static Strength Design criterion, and the rigidity requirement of structure is low, the rigidity of material can meet structural requirement automatically, carry out contrast sequence according to the ratio static strength of candidate materials, the material more maximum than static strength is optimum;
Only referring to structure according to rigidity Design criterion reaches rigidity Design index, and material can meet static strength requirement automatically, only needs to carry out contrast sequence according to the stiffness-to-density ratio of candidate materials, the material optimum that stiffness-to-density ratio is maximum;
Only referring to structure according to damage tolerance design criterion reaches damage tolerance design index, and material can meet structure at the static strength contained under crackle state and rigidity requirement, carry out contrast sequence according to the ratio toughness of candidate materials, the material more maximum than toughness is optimum;
Only refer to when structure reaches durability Design index according to durability Design criterion, and material therefor meets static strength and rigidity requirement, then carry out contrast sequence according to the ratio strength at repeated alternation of candidate materials, the material mechanical performance more maximum than strength at repeated alternation is optimum;
Only refer to when structure reaches safe-life design index according to safe-life design criterion, and material therefor meets static strength and the rigidity requirement of structure, carry out contrast sequence according to the ratio strength at repeated alternation of candidate materials, the material more maximum than strength at repeated alternation is optimum;
According at least two kinds of design criterias, then according to the ratio of design objective corresponding to each design criteria, contrast sequence to be carried out according to fatigue ratio, quiet tough ratio or tired tough ratio.
For not load-carrying construction, meet the prerequisite of structure function demand at material under, only need to carry out contrast sequence according to the density of material, the minimum material of density is optimum.
Only by the structure of static strength criterion design, it is generally the structure of the cyclic loading being only subject to the structure of static load or being only subject to little number of times load little in life cycle management, and the rigidity requirement of structure is not high, the rigidity of material generally can meet structural requirement automatically, only need to carry out contrast sequence according to the ratio static strength of candidate materials, the material more maximum than static strength is optimum.
Only by the structure mainly excessive failure mode caused of structural distortion of stiffness criterion design, when structure reaches rigidity Design index, material generally can meet static strength requirement automatically, only needs to carry out contrast sequence according to the stiffness-to-density ratio of candidate materials, the material optimum that stiffness-to-density ratio is maximum.
Only press the structure of safe life criterion design, when structure reaches safe-life design index, if material therefor can meet static strength and the rigidity requirement of structure, only need to carry out contrast sequence according to the ratio strength at repeated alternation of candidate materials, the material more maximum than strength at repeated alternation is optimum.
Only press the structure of durability criterion design, when structure reaches durability Design index, if material therefor can meet static strength and rigidity requirement, can carry out contrast sequence according to the ratio strength at repeated alternation of candidate materials, the material mechanical performance more maximum than strength at repeated alternation is optimum; Due to the ability that structure durability is structure opposing cracking, burn into thermal fatigue, stripping, wearing and tearing and Foreign Object Damage, for the structure selection of privileged sites, need on the basis of material mechanical performance, the indexs such as anticorrosive aging, thermal fatigue, the hardness of bond material consider.
Only press the structure of damage tolerance criterion design, when structure reaches damage tolerance design index, if material can meet structure containing the static strength under crackle state and rigidity requirement, only need to carry out contrast sequence according to the ratio toughness of candidate materials, the material optimum more maximum than toughness.
For simultaneously according to the structure of at least two kinds of criterions designs, selection material should in line with material property and the harmonious principle of each design objective, otherwise, some index of material may be caused just to reach designing requirement, and other indexs are significantly beyond design, so not only can cause the waste of some performance figure of material, and the weight of structure can be increased due to the restriction of material " short slab " index.Therefore, first to lay particular stress on degree, the ratio of the design objective that namely each design criteria is corresponding according to each design criteria, reduce the scope of candidate materials according to fatigue ratio, quiet tough ratio or tired tough ratio further.Above-mentioned three parameters, what fatigue ratio was investigated is safe life criterion or lays particular stress on degree between durability criterion and static strength criterion; Quiet tough be the degree that lays particular stress between damage tolerance criterion and static strength criterion than what investigate; Tired tough be lay particular stress on degree between damage tolerance criterion and safe life criterion or durability criterion than what investigate.
Within the scope of candidate materials after reducing, according to the structural design criterion laying particular stress on most i.e. override guarantee, be as the criterion with the material property parameter of its correspondence and carry out material sequence, the material that performance figure are larger is more excellent.Wherein, the material property parameter that static strength criterion is corresponding is than static strength; Material property parameter corresponding to stiffness criterion is stiffness-to-density ratio; Safe life criterion and material property parameter corresponding to durability criterion are than strength at repeated alternation; Material property parameter corresponding to damage tolerance criterion is than toughness.
Strength-to-density ratio is referred to, namely γ than static strength
σ/ρ, unit is Nm/kg, refers to the tensile strength sigma of material
bwith the ratio of density of material ρ, i.e. γ
σ/ρ=σ
b/ ρ, the tensile strength sigma of material
brefer to limit stress during Materials Fracture, reflect the fracture resistance of material, unit is MPa, and the ratio static strength of material is higher shows that the structure quality of materials used when reaching corresponding static strength is lighter.
Stiffness-to-density ratio is exactly γ
c/ ρ, unit is Nm/kg, refers to the elastic modulus E of material and the ratio of density of material ρ, i.e. γ
e/ ρ=E/ ρ; Wherein, the elastic modulus E of material characterizes the deflection size of material under a certain state of stress, reflects the non-deformability of material, modulus of elasticity is larger, deflection is less, and unit is MPa, and the stiffness-to-density ratio of material shows that more greatly the structure quality of materials used when reaching corresponding rigidity is lighter.
Be exactly γ than toughness
k/ ρ, unit is
refer to the fracture ductility K of material
iCwith the ratio of density of material ρ, i.e. γ
s/ ρ=K
iC/ ρ, fracture ductility K
iCrefer to the critical stress intensity factors containing cracked material crackle generation unstable propagation under opening mode crack pattern and plane strain state, characterize the ability of material Anticrack, be the standard of tolerance toughness of material quality, unit is
Be exactly γ than strength at repeated alternation
s/ ρ, unit is Nm/k
8, refer to the fatigue limit S of material
-1with the ratio of density of material ρ, i.e. γ
s/ ρ=S
-1/ ρ, the fatigue limit S of material
-1refer under the constant-amplitude fatigue loading of stress amplitude ratio R=-1, material can bear unlimited cycle of stress and the maximum stress of destruction not occur, that reflects the level of material repels fatigue cracking or fatigue of material performance, unit is MPa, and the ratio strength at repeated alternation of material is higher shows that the structure quality of materials used when reaching corresponding strength at repeated alternation is lighter.
Fatigue ratio is exactly γ
s/ σ, be characteristic, refer to the fatigue limit S of material
-1with tensile strength sigma
bratio, i.e. γ
s/ σ=S
-1/ σ
b, what what fatigue ratio represented was between durability criterion and Static Strength Design criterion lays particular stress on degree; Fatigue ratio reflects the proportionate relationship of fatigue of material intensity and static strength, and the fatigue ratio of material is larger, and illustrate that the structure be made up of material is when reaching corresponding static strength and requiring, the ability of structure resisting fatigue cracking is stronger, and fatigue property is better.
Quiet tough ratio is exactly γ
s/ σ, unit is
refer to the fracture ductility K of material
iCwith tensile strength sigma
bratio, i.e. γ
k/ σ=K
iC/ σ
b, quiet tough be the degree that lays particular stress between damage tolerance design criterion and Static Strength Design criterion than what represent; Quiet tough ratio reflects the fracture ductility of material and the proportionate relationship of static strength, and the quiet tough ratio of material is larger, and illustrate that the structure be made up of material is when reaching corresponding static strength and requiring, after structure crack, the ability of resisting fatigue crack is stronger.
Tired tough ratio is exactly γ
k/s, unit is
refer to the fracture ductility K of material
iCwith fatigue limit S
-1ratio, i.e. γ
k/s=K
iC/ S
-1tired tough ratio reflects the fracture ductility of material and the proportionate relationship of strength at repeated alternation, the tough ratio of fatigue of material is larger, illustrate that the structure be made up of material is when reaching corresponding strength at repeated alternation and requiring, the ability that structure resists the unexpected destruction caused by endurance crack is stronger, and the fail-safety of structure is better.
As shown in Figure 1, the first step: the structure objects determining selection, the structure objects of selection is the wing crossbeam of certain blimp, and wing crossbeam is one of main force support structure of aircraft, and its generation fracture failure or deformation failure directly can affect the flight safety of aircraft.
Second step: determine structure function and designing requirement, the large beam action one of wing is load effect, and it bears the deadweight of aerodynamic loading that each parts of wing transmit and wing tank; Two is intermal forces, by suffered dynamic changes process to fuselage, provides lift upwards when taking off to fuselage, when aircraft is parked to the downward pressure of fuselage transmission and corresponding moment of flexure; Three is the aerodynamic configurations keeping wing, makes the distortion of wing maintain in certain scope, to ensure pneumatic fail not to occur.Because this wing crossbeam is made through overall milling, specific requirement is had to the delivery dimension of material, require that raw MAT'L cross section is at least not less than 200mm × 60mm, length is not less than 4m, if the outer protective system of wing crossbeam lost efficacy, it will be subject to the effect of stress corrosion when aircraft parked state, tired effect is corroded when aircraft low flies, from the angle of safety, require that the stress corrosion cracking toughness making crossbeam material is greater than 10, the operating temperature interval of wing crossbeam is-55 DEG C to 80 DEG C.
3rd step: determine structure importance and maintenance cost, structure importance refers to the influence degree to flight safety after structural failure.
4th step: determine structure stress situation and functional requirement.
5th step: according to structure importance and maintenance cost determination structural design criterion, according to the design requirement initial setting candidate materials scope of aircaft configuration, is setting candidate materials scope further according to structure stress situation, functional requirement.
Owing to directly affecting flight safety, wing crossbeam is designed to fail safe structure, namely adopts damage tolerance design criterion; From the angle of economic repair, wing crossbeam adopts durability Design criterion simultaneously; In addition, the design of wing crossbeam needs to meet static strength and rigidity requirement, the particularly crackle ultimate limit state when reaching critical length soon simultaneously and still will meet above-mentioned requirements.
As the main force support structure of aircraft, from the viewpoint of the mechanical property of material, candidate materials is divided into four classes, is steel, aluminum alloy, titanium alloy and composite material respectively.
Because the steel meeting structural static strength requirement are high strength steel, and the general counter stress of high strength steel is concentrated responsive, and fail-safety is poor, and difficulty of processing is large, is rejected by steel; Because titanium alloy counter stress is concentrated also very sensitive, and material cost is high, is rejected by titanium alloy; Consider from the angle of economy, later maintenance, manufacture of materials technology maturity and material fiduciary level, composite material is rejected.Therefore, the material primary election scope of this aircraft wing crossbeam structure is aluminum alloy.
Within the scope of all aviation alloyed aluminiums, because 6000 of heat treatment type alloy in the nonheat-treatable alloy in cast aluminium alloy, deforming aluminium alloy and deforming aluminium alloy is that al-mg-si alloy is relative general with some mechanical property of 8000 line aluminium alloys, be not suitable as the main force support structure of aircraft, therefore rejected.After taking turns screening second, it be Solder for Al-Cu Joint Welding Alclad, 7000 is aluminium-zinc-magnesium-copper extra super duralumin alloy that the alternative scope of material of this aircraft wing crossbeam structure is contracted to 2000 further.
Be Solder for Al-Cu Joint Welding Alclad, 7000 2000 be in aluminium-zinc-magnesium-copper extra super duralumin alloy, because the material shear strengths such as 2A01,2A10,2B16 are larger; 2A02,2A16,2A70,2014, at high temperature mechanical property is better for the material such as 2618A; The materials such as 2A14 at low temperatures mechanical property are better; The materials hot working better performances such as 2A50,2B50; The material welding performances such as 2A11 are better; The material corrosion resistance such as 7A33 are better, and the design of these materials above-mentioned is mainly in order to meet the specific demand of structure, and its mechanical performance index is relatively general, is also not suitable as the main force support structure of aircraft, is therefore rejected.In addition, again due to the processing request that can not meet wing crossbeam for delivery gauge of the materials such as 2014,2124,2524,7050, also rejected.
Through third round screening after, the structure selection range finally determined is: 2A12,2024,7A04,7A09,7075 and 7475, the supply of material state under its correspondingly-sized is T4, T3510, T6, T73, T73510 and T7351 respectively.
6th step: carry out material contrast according to the load characteristic of structure, at least one structural design criterion, candidate materials scope and sort, as shown in Figure 2, because wing crossbeam is according to damage tolerance criterion and the design of durability criterion, and demand fulfillment static strength and rigidity requirement.Therefore, should mainly according to being according to carrying out the sequence of material than toughness with than this two indices of strength at repeated alternation.The ratio static strength of all candidate materials and stiffness-to-density ratio all can reach Structural Design Requirement.Obviously, 7475-T7351 material is being optimum than toughness with than on this two indices of strength at repeated alternation.7075-T73510 and the 7A09-T73 bi-material taken second place is compared, the ratio fatigue strength values of 7075-T73510 is higher, and the ratio toughness values of 7A09-T73 is higher, because wing crossbeam concerns flight safety, more bias toward damage tolerance design criterion, therefore, the 7A09-T73 sequence second that tired tough ratio is higher.Remaining material sequence is 7075-T73510,7A04-T6,2024-T3510 and 2A12-T4 respectively.
7th step: carry out Material selec-tion, the most forward 7475-T7351 aluminum alloy of selected and sorted carries out the checking of every structure design demand as first material selection.
8th step: judge whether selected materials meets structure design, manufacture, operating needs, 7475 aluminum alloys are aluminium-zinc-magnesium-copper system heat treatment reinforcement aluminum alloys, its corrosion resistance is suitable with 7075 aluminum alloys, and T7351 state is compared compared with other state, the performance of abrasion and stress corrosion is higher, its stress corrosion cracking toughness is 25.7, meets design requirement.This material can be produced at home, meets economic index; And there is good process plastic and superplasticity, there is good forming characteristics, meet the requirement of processing technology and structural repair.Every material performance index of this material (-55 DEG C) at low temperatures declines little; And the long-time military service under maximum operation temperature (80 DEG C) can be ensured, meet the structure performance assessment criteria at varying environment temperature.
If selected materials meets structure design, manufacture, operating needs, then carry out determining the final selection of structure, if selected materials does not meet structure design, manufacture, operating needs, then re-start Material selec-tion, until selected materials meets structure design, manufacture, operating needs, thus determine the final selection of structure, if re-start Material selec-tion, selected materials still cannot meet structure design, manufacture, operating needs, then the function that restructures and designing requirement.Through the checking of the 7th step, 7475-T7351 aluminum alloy meets the choice requirement of aircraft wing crossbeam, determines that this material is final selection.
The present invention improves evaluation of material system and reasonably determines that aircaft configuration selection provides Theories and methods support, thus aircraft utilization economy is improved under the prerequisite ensureing flight safety and aircraft technology index, the present invention is on the basis that ensure that aircraft structure strength requirement, carry out rational material selection, not only can ensure the military service safety in utilization of aircaft configuration, and can aero-structure weight be alleviated, improve airworthiness, reduce use cost, the series material performance figure that the present invention proposes, not only can realize the mechanical property contrast between different materials, and can reflect that material lays particular stress on degree in different mechanical properties, examination and the critical for the evaluation of material are quantized, and can apply and other field except aviation field, applied range.
It should be noted that above what enumerate is only a kind of specific embodiment of the present invention.Obviously, the invention is not restricted to above embodiment, many distortion can also be had.
In a word, all distortion that those of ordinary skill in the art can directly derive from content disclosed by the invention or associate, all should think protection scope of the present invention.
Claims (10)
1., based on an aircaft configuration selection method for series material performance figure, it is characterized in that, the method comprises the following steps:
1) according to the structure objects of the design requirement determination selection of aircaft configuration;
2) structure function and designing requirement is determined;
3) structure importance and maintenance cost is determined;
4) structure stress situation and functional requirement is determined;
5) determine five kinds of structural design criterions according to structure importance and maintenance cost, according to the design requirement initial setting candidate materials scope of aircaft configuration, set candidate materials scope further according to structure stress situation, functional requirement;
6) carry out material contrast according to the load characteristic of structure, at least one structural design criterion, candidate materials scope and sort;
7) Material selec-tion is carried out;
8) judge whether selected materials meets structure design, manufacture, operating needs, if selected materials meets structure design, manufacture, operating needs, then carry out determining the final selection of structure, if selected materials does not meet structure design, manufacture, operating needs, then re-start Material selec-tion, until selected materials meets structure design, manufacture, operating needs, thus determine the final selection of structure, if re-start Material selec-tion, selected materials still cannot meet structure design, manufacture, operating needs, then the function that restructures and designing requirement.
2. a kind of aircaft configuration selection method based on series material performance figure according to claim 1, is characterized in that, the structure objects of described selection is the composition structure forming airframe or the structure that can threaten to flight safety when it lost efficacy.
3. a kind of aircaft configuration selection method based on series material performance figure according to claim 1, is characterized in that, described structure function comprise load, power transmission, maintenance aircraft aerodynamic configuration, form specific local space.
4. a kind of aircaft configuration selection method based on series material performance figure according to claim 1, is characterized in that, described structure importance is the influence degree to flight safety after aircaft configuration lost efficacy.
5. a kind of aircaft configuration selection method based on series material performance figure according to claim 1, it is characterized in that, described structural design criterion is take different design criterias for Different factor, and described five kinds of structural design criterions comprise Static Strength Design criterion, rigidity Design criterion, damage tolerance design criterion, durability Design criterion, safe-life design criterion.
6. a kind of aircaft configuration selection method based on series material performance figure according to claim 5, it is characterized in that, described factor comprises load-carrying construction, need avoid the structure producing Aeroelastic Problems maybe can not occur excessive deformation so that affect the structure of aeroplane performance, the crucial load-carrying construction of aircraft, the angle of economy, superhigh intensity steel structure in aircraft, the structure of inspection and maintenance is not easy in aircraft, describedly take Static Strength Design criterion according to load-carrying construction, avoid producing the structure that the structure of Aeroelastic Problems maybe can not occur excessive deformation so that affect aeroplane performance as required and take rigidity Design criterion, damage tolerance design criterion taked by crucial load-carrying construction according to aircraft, durability Design criterion is taked according to the angle of economy, safe-life design criterion is taked according to the superhigh intensity steel structure in aircraft, safe-life design criterion is taked according to the structure being not easy to inspection and maintenance in aircraft.
7. a kind of aircaft configuration selection method based on series material performance figure according to claim 1, it is characterized in that, described aircaft configuration design requirement comprises load bearing requirements, weight demands, volume requirement, resistance to corrosion requires, fail-safety requires, welding performance, penetrability require, thermal environment requires, electromagnetic wave shielding requires, insulativity requires, cost requirement.
8. a kind of aircaft configuration selection method based on series material performance figure according to claim 7, it is characterized in that, described according to the scope of penetrability requirement initial setting candidate materials scope at translucent material, require that initial setting candidate materials scope is in the scope of heat-resisting material according to thermal environment, require that initial setting candidate materials scope is in the scope without electromagnetic shielding material according to electromagnetic wave shielding, according to without design requirement initial setting candidate materials scope in steel, aluminum alloy, titanium alloy, composite material.
9. a kind of aircaft configuration selection method based on series material performance figure according to claim 5, is characterized in that,
Described according to Static Strength Design criterion refer to only by the structure of static load or in life cycle management by the structure of the large cyclic loading of load, and the rigidity requirement of structure is low, the rigidity of material can meet structural requirement automatically, carry out contrast sequence according to the ratio static strength of candidate materials, the material more maximum than static strength is optimum;
Described refers to structure according to rigidity Design criterion and reaches rigidity Design index, and material can meet static strength requirement automatically, only needs to carry out contrast sequence according to the stiffness-to-density ratio of candidate materials, the material optimum that stiffness-to-density ratio is maximum;
Described refers to structure according to damage tolerance design criterion and reaches damage tolerance design index, and material can meet structure at the static strength contained under crackle state and rigidity requirement, carry out contrast sequence according to the ratio toughness of candidate materials, the material more maximum than toughness is optimum;
Described refers to when structure reaches durability Design index according to durability Design criterion, and material therefor meets static strength and rigidity requirement, then carry out contrast sequence according to the ratio strength at repeated alternation of candidate materials, the material mechanical performance more maximum than strength at repeated alternation is optimum;
Described refers to when structure reaches safe-life design index according to safe-life design criterion, and material therefor meets static strength and the rigidity requirement of structure, carry out contrast sequence according to the ratio strength at repeated alternation of candidate materials, the material more maximum than strength at repeated alternation is optimum;
Described basis at least two kinds of design criterias, then according to the ratio of design objective corresponding to each design criteria, will carry out contrast sequence according to fatigue ratio, quiet tough ratio or tired tough ratio.
10. a kind of aircaft configuration selection method based on series material performance figure according to claim 9, is characterized in that,
Describedly refer to strength-to-density ratio than static strength, namely γ
σ/ρ, refer to the tensile strength sigma of material
bwith the ratio of density of material ρ, i.e. γ
σ/ρ=σ
b/ ρ, the tensile strength sigma of described material
brefer to limit stress during Materials Fracture;
Described stiffness-to-density ratio is exactly γ
e/ ρ, refer to the elastic modulus E of material and the ratio of density of material ρ, i.e. γ
e/ ρ=E/ ρ;
Described is exactly γ than toughness
k/ ρ, refer to the fracture ductility K of material
iCwith the ratio of density of material ρ, i.e. γ
k/ ρ=K
iC/ ρ;
Described is exactly γ than strength at repeated alternation
s/ ρ, refer to the fatigue limit S of material
-1with the ratio of density of material ρ, i.e. γ
s/ ρ=S
-1the fatigue limit S of material described in/ρ
-1refer under the constant-amplitude fatigue loading of stress amplitude ratio R=-1, material can bear unlimited cycle of stress and the maximum stress of destruction not occur, and that reflects the level of material repels fatigue cracking or fatigue of material performance;
Described fatigue ratio is exactly γ
s/ σ, refer to the fatigue limit S of material
-1with tensile strength sigma
bratio, i.e. γ
s/ σ=S
-1/ σ
b, what what described fatigue ratio represented was between durability criterion and Static Strength Design criterion lays particular stress on degree;
Described quiet tough ratio is exactly γ
k/ σ, refer to the fracture ductility K of material
iCwith tensile strength sigma
bratio, i.e. γ
k/ σ=K
iC/ σ
b, described quiet tough be the degree that lays particular stress between damage tolerance design criterion and Static Strength Design criterion than what represent;
Described fatigue is tough, and ratio is exactly γ
k/s, refer to the fracture ductility K of material
iCwith fatigue limit S
-1ratio, i.e. γ
k/s=K
iC/ S
-1, described fatigue is tough than representing is lay particular stress on degree between damage tolerance design criterion and safe-life design criterion or durability criterion.
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