CA2399499A1 - Universal horizontal impact tester - Google Patents

Abstract

This invention provides a mufti-purpose apparatus for delivering a well-defined quantity of mechanical energy to a specimen. In the collision embodiment, the apparatus is a two-car compression specimen tester. Cars are propelled by gravity on the same set of oppositely inclined rails that merge into horizontal segments where collision occurs.
This allows the kinetic energy of the cars to be dissipated into a compression specimen carried by one of the cars. Car release height affects the initial velocity of a car at impact. Car release height and car mass affect impact energy. In the sweep embodiment, the cars ride on separate tracks.
One car grips a fracture specimen while the other carries a tup. The kinetic energy of the cars is partly dissipated into the fracture specimen. The specimen fracture energy is determined by measuring the initial and final height of the center of mass of each car.

Description

*** Note: Data on abstracts and claims is shown in the official language in which it was submitted.
(72) Inventors (Country): SEAMAN, DARRYL W. (Canada) (~3) Owners (Country): SEAMAN, DARRYL W. (Canada) f71) Anulicants (Country): SEAMAN, DARRYL W. (Canada) (45) Issued:
(22) Filed:
(43) Laid Open:
(5i) International Class (IPC):
Patent Cooperation Treaty~PCT): Yes (85) National Entry:
(86) PCT Filing number: 2 (8'7) International publication number:

Disclosures Image r Drawings Image r Representative Drawing Image .;,.
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References Cited (Referenced Byl U.S. Patent Documents 4085609 Apr., 1978 Kelly Other References ( 1 ) INSTRON CANADA TNC, Private Communication, 2001.

(2) INSTRON-SATEC Systems, SI-1 Series Impact Testing System Document Number 000052-03-0700, p12.

(3) Y. Yamaguchi, S. Takagi, and H. Nakano, Effects of Anvil Configuration on Absorbed Energy, p164, in Pendulum Impact Testing: A Century of Progress, T.A. Siewert and M. Manahan, editors, ASTM (2000) (4) G. Charily, Essay on the Metal Impact Bend Test of Notched Bars (Reprint from 1901 ), p46, in Pendulum Impact Testing: A Century of Progress, T.A.
Siewert and M. Manahan, editors, ASTM {2000) (5) E. Siebel and G. Pomp, Die Ermittlung der Formanderungsfestigkeit von Metallen durch den Stauchversuch, Mitt. Kaiser-Wilhelm Inst. Eisenforsch, vol 9, p157, Diisseldorf, 1927 Part Numbering Scheme Sample 1 Tup or Striker 2 Left Car or Lower Car 3 Right Car or Upper Car 4 Lower Track S

Upper Track 6 Straight Track Segment 7 Left Inclined track 8 Segment Right Inclined Track 9 Segment Platen 10 Flat Die 11 Pocket Die 12 Funnel 13 Calorimeter 14 Recess 15 Holder 16 Paraffin 17 S

Universal Horizontal Impact Tester (ITHIT) 1.0 Introduction 1.1 Collision Embodiment 1.2 Sweep Embodiment 2.0 Novelty and Usefulness of Invention 2.1 Introduction 2.2 Foundation Work Issues 2.2.1 Foundation Work for Drop-Weight Impact Tester 2.2.2 Foundation Work for Pendulum Impact Tester 2.3 Energy Balance Issues 3.0 Implementations of Universal Horizontal Impact Tester 3.1 Introduction 3.2 Collision Embodiment of Impact Tester 3.2.1 Introduction 3.2.2 Physical Simulation of CHQ Process 3.2.3 Modeling of Material Flow Stress 3.3 Sweep Embodiment of Impact Tester 3.3.1 Introduction 3.3.2 Charpy Impact Energy Determination 3.3.3 Izod Impact Energy Determination 3.3.4 Skelp Impact Energy Determination 3.3.5 Bolt Head Decapitation Energy Determination 3.3.6 Tensile Impact Energy Determination 1.0 Introduction My invention relates generally to the testing of materials, in particular, materials of a metallic or plastic nature. It provides a mufti-purpose apparatus for applying a well-defined quantity of mechanical energy to a specimen. The apparatus has two main embodiments: the collision embodiment and the sweep embodiment.
1.1 Collision Embodiment In the collision embodiment, the Universal Horizontal Impact Tester (UHIT) is a two-car compression specimen tester. It is used for:
~ Physical Simulation of Cold Heading Process ~ Constitutive Modelling of Material Flow Stress The teachings of my invention can be readily understood by considering the following description in conjunction with the accompanying drawing, Figure A.
Figure Al is a perspective view of two cars immediately before impact on the horizontal portion of the track.
Figure A2 is a side elevation of the two cars in the armed position, along with dimensions used in building a particular Universal Horizontal Impact Tester.
Cars (3) and (4) are raised to the desired height at the ends of oppositely inclined track segments (8) and (9) that blend into a horizontal segment (7), and are latched in the armed position. The cars, which ride on the same track, are released, and move down the inclined segments of the track, propelled by gravity. During the collision event in the middle of the horizontal track segment, the kinetic energy minus the elastic energy stored in the cars is dissipated into a specimen carried by one of the cars. The specimen generally falls out of the dies following the recoil of the cars, and can be conveniently funneled into a calorimeter to ascertain the total absorbed energy.
The relation governing the velocity, V, of an object falling in a gravitational field is:
_~ g( v2 V 2 H;n;t;a~ -Hfinal)~
Here, g is the gravitational constant, and H is the initial height of the object. This relation is well known to those practiced in the art of mechanical testing. My invention allows the initial impact velocity seen by the compression specimen to be set easily by adjusting the heights of the two cars in the armed position on the inclined segments of the track.
The cars are set at equal heights to minimize residual momentum. The relative velocity between the two cars is:
V = 2 ~2g (H~nitial -H&nal)~ 1/2 The relation governing the energy, E, of an object falling in a gravitational field is:
E = Mg (H;nitial -Hfinal) Here M is the mass of the object. This relation is also well known to those practiced in the art of mechanical testing. My invention allows the impact energy applied to the compression specimen to be easily set by adjusting the initial heights of the two cars in the armed position on the inclined segments of the track and/or by changing the mass of the cars. Again the cars are set at equal height, and are allotted equal mass, to minimize residual momentum.
The total energy available from both cars is:
E = 2 Mg (H;nitial -Hfinat) Here, M is the mass of a single car. An overwhelming fraction of the energy E
is delivered to the specimen. A small fraction is stored as elastic energy in the cars and specimen, and is restituted after impact, and thence dissipated in friction as the cars undergo a minor rebound. The energy applied to the specimen can be calculated net of energy dissipated in friction by allowing one car to travel, unimpeded, down one incline and up the other. For each car, the intensive friction loss, eF, that is, the energy lost in friction per metre of car travel, Lfr~ ~a"el, is determined by measuring the difference between the initial height, H;n;~;a~, of the mass centroid of the car, and the final height, Hapogee, of the mass centroid of the car at its apogee, with reference to a datum, Hdacum:
eF = M g yHinitial - Hdatum) - (Hapogee - Hdat~I~ Lfree travel where, as before, M is the mass of the car. The latter relation can be simplified, of course, to:
eF = M g ~Hinitial - Hapogee~~ I-free travel The extensive formulation for eF , that is the total energy lost in friction, EF, can be written:
EF = M g ~H;n;t;~ - Hapogee~ Limpact ~ Lfree travel where L;n,pa~t is the centroid to centroid distance between a car in the armed position, and the car at the point of impact, measured along the track.
In a properly constructed horizontal impact tester, the cars are so evenly matched that it is sufficient to determine EF for one car only. Neglecting the small amount of sound, heat and elastic energy, the energy delivered to a compression specimen, E, is calculated using a relation easily derived by those practiced in the art of mechanical testing:
E = 2 Mg (H;n;tial -Hfinal) - 2M g ~H;nitial - Hapogee~ Limpact ~ Lfree travel g E = 2 [Mg (Hinitial - Hfinal) - EF
The factor 2 accounts for the fact that there are two cars. The small but inevitable elastic recoil following collision may be readily determined using the formulation given in Section 2.3, where more subtle issues of energy balance are discussed.
For finer measurement of mechanical variables, such as energy, force and acceleration, and in particular where information is desired at various segments of the impact history, it is possible to instrument the horizontal impact tester using accelerometers and/or load cells attached to one or two cars, as is conventionally practiced.
1.2 Sweep Embodiment In the sweep embodiment, the Universal Horizontal Impact Tester is a two-car fracture specimen tester. It is used for:
~ Charily Specimen Impact Energy Determination o Standard and Subsize Charily o Charily V-Notch Specimens ~ Impact Testing of Large-Size Skelp V-Notch Specimens ~ Izod Specimen Impact Energy Determination ~ Fastener Head Impact Testing ~ Tensile Specimen Impact Testing The teachings of my invention can be readily understood by considering the following description in conjunction with the accompanying drawing, Figure B, in which like numerals denote like parts throughout the two views. This particular sweep embodiment, the Charily Specimen Impact Tester, is discussed at greater length in Section 3.3.2.
Figure B 1 is a perspective view of two cars mounted on their respective tracks.
Figure B2 is a front elevation view of the two cars of Figure B 1.
The configuration of the sweep embodiment of the horizontal impact tester departs significantly from that of the collision embodiment, in that the two cars (3) and (4) travel on separate tracks (5) and (6), respectively. The rails of the outer track (6) straddle the rails of the inner track (5). In some embodiments, the car carrying a fracture specimen ( 1 ) rides on the outer track (6), while the car to which is attached a tup (2) rides on the inner track (5). In other embodiments, the car to which is attached the tup rides on the outer track, while the car which holds the fracture specimen rides on the inner track. The tracks merge into their respective horizontal segments (7). Cars are set at equal heights are released, and thence propelled by gravity towards their respective horizontal track segments where impact between the fracture specimen and the tup occurs. The specimen normally fractures, allowing the cars to sweep past one another, and travel up the opposite inclined track segments. The impact energy absorbed by the fracture specimen is a function of the sum of the differences between initial and final heights of the mass centres of the cars. The specimen pieces are normally thrown clear of the cars.
As in the collision embodiment of the universal horizontal impact tester, the energy dissipated in friction can be calculated by allowing a car to travel unimpeded down one incline and up the other:
eF = M g ~Hinitial ' Hapogee~~ Lffee travel As mentioned above, the cars are so evenly matched in a properly constructed horizontal impact tester that it is generally sufficient to determine eF for one car only. Within a small error comprising sound, heat and elastic energy inevitably stored in the cars, the energy applied to a compression specimen, E, is calculated using the relation:
E - lVlg ~Hl,initial - Hl,final~ - eF Lla + lVlg ~H2,initial - H2,final~~ - eF
L2a where Lla is the centroid to centroid distance between car 1 in the armed position, and car 1 at its apogee, measured along the track, and L2a is the centroid to centroid distance between car 2 in the armed position, and car 2 at its apogee, measured along the track.
Here, Hl,;",t~~ and Hl,fnal are initial height and final height of car 1, while HZ,;n,u~ and HZ,f,~~ are initial height and final height of car 2. In general, Hl,;n~t;a~
and H2,;n~t~a~ are made equal, and can therefore be written H;n;t~al, so that the above relation simplifies to:
E - lVlg C2 Hlnitial - ~Hl,final+ H2,final ~~ - ~eF Lia ~ eF L2a The elastic recoil energy can be calculated as explained in Section 2.3, and subtracted from the right hand side of the previous equation.
For finer measurement of mechanical variables, such as energy, force and acceleration, and in particular where information is desired at various segments of the impact history, it is possible, of course, to instrument the horizontal impact tester using accelerometers and/or load cells attached to one or two cars, as is conventionally practiced.
It should be obvious that both collision and sweep embodiments of the horizontal impact tester can be implemented on the same frame.
2.0 Novelty and Usefulness of Invention 2.1 Introduction It should by now be readily apparent and appreciated by those practiced in the art and science of mechanical testing of materials that the novelty and usefulness of my invention resides in the fact that its design and operation are in harmony with the laws of physics, in particular, with the laws of classical Newtonian mechanics. In the following sections, foundation work and energy balance issues are addressed.
2.2 Foundation Work Issues 2.2.1 Foundation Work for Drop-Weight Impact Tester One major consequence of my design is that no foundation work is required, neither in the collision embodiment nor in the sweep embodiment of my universal horizontal impact tester. In fact, it is entirely possible, and in some cases desirable, to house the equipment on a mobile platform, which may be readily hauled from location to location.
The advantages brought about by my invention become clear when one considers the foundation work required for conventional impact testers.
In conventional drop-weight testers, collision occurs between a tup and a fixed specimen.
These testers must be carefully designed to provide maximum protection for the instrumented tup and the test specimen. This protection is required to prevent overloading of the instrumented tup after fracture of the test specimen. The design consists of stop blocks and/or shocks, which repel the crosshead after the test specimen fractures, and catch the tup. The design of the equipment must also minimize the adverse shock, which can be transmitted to the components located in the control housing. The drop-weight system must be securely bolted to a rigid foundation to permit maximum utilization of these design features and prevent damage to critical components.
The functions of the foundation are firstly, to provide a rigid mass through which the shock is absorbed and dissipated into the earth, and secondly, to provide a flat, level surface to which the drop-weight system can be affixed. The foundation must have sufficient contact area with the earth to prevent undue settling. If a rigid foundation is not provided, alterations in the test data, premature failure of the equipment, and excessive vibration causing spring action, can occur. Guidelines are provided by manufacturers of drop-weight testers to assist in the installation of their equipment. The mass of a rigid foundation must be ten times greater than the crosshead mass impacting the test specimen and stop blocks. For example, a crosshead mass of 1000 kg calls for a foundation of 10,000 kg, which if constructed of steel-reinforced concrete equates to a block 2 m wide, 2m deep and 1.25 m high [ 1 ]. The static load bearing capacity of the soil for the location of each impact tester must be determined by a local soil engineer, taking into consideration that the dynamic impact loads should not exceed the static load of the soil. Moreover, the foundation should have sufficient contact area with the soil to prevent undue settling. Manufacturers generally recommend that the slab be isolated from the surrounding floor to alleviate any potential vibration to equipment located in close proximity. In particular, it is very important that the drop-weight system be carefully secured to a steel mounting plate built into the foundation. The recommended procedure is to carefully level the mounting plate and use a very thin layer of epoxy filler between the mounting plate and drop-weight system base plate to secure a good integral fit between these two components. It is most important that the crosshead drops in a vertical path and thereby minimizes friction caused by the interaction with the guide columns.
2.2.2 Foundation Work for Pendulum Impact Tester Pendulum impact testers, where a tup impacts a fixed specimen and sweeps by, are analogous to the sweep embodiment of my universal horizontal impact tester.
Again, foundations for pendulum impact testers must be carefully designed or the following problems can arise: alterations in the test data; premature failure of equipment; and excessive vibration causing spring action. A typical foundation for a commercially available 400 J pendulum impact tester [2] consists of a block 1.5 m wide, lm deep and 0.5 m high, which amounts to 1500 kg. A 500 Joule C-type pendulum tester is documented by Yamaguchi, Takagi and Nakano [3]. The machine is fixed on a 1.5 m wide, 1 m deep and 0.1 m thick steel block foundation, which is embedded in a concrete floor to ensure rigid mounting of the machine. A block of steel of these dimensions weighs 1200 kg. As yet another example, Charpy [4] describes a pendulum tester with a 50 kg striker plate. The anvil-bed weighs 1600 kg. It is driven into the ground and cemented into a masonry block of 5 m weighing 10,000 kg.
2.3 Energy Balance Issues A second major consequence of my design is that, in contradistinction with conventional designs, a greater portion of the available potential energy of the tup is directed at the test specimen. In conventional designs, the foundation yields elastically and plastically in a rather indeterminate manner, absorbing energy not dissipated in the specimen, and interfering with acceleration/time or force/time measurements on the specimen.
In my novel design, the losses are much more circumscribed. For example, the elastic recoil energy of a car in the collision mode can be calculated using the following relation, which is obvious to those practiced in the art of mechanical testing:
Energy absorbed during recoil = Potential energy + Friction Energy Erebound - Mg [Hrecoil - Hcollision] + eF Lrecoil Here, M is the mass of the car, g is the gravitational constant, Hrebound is the height of the center of mass of the car above a reference level on the horizontal segment of track at the apogee of the recoiling car, Heollision is the height of the center of mass of the car above a reference level on the horizontal segment of track at the moment of collision, and Lre~oil is the distance travelled along the track by the recoiling car. The symbol eF is the intensive friction loss, that is, the energy lost in friction per metre of car travel, and retains the precise definition given in Section 1.1.

3.0 Implementations of Universal Horizontal Impact Tester 3.1 Introduction In the following, details of seven implementations of the UHIT are given.
These are not limiting, in the sense that additional implementations that do not deviate significantly from the scope of my invention are possible. The seven implementations clearly attest to the universality of my invention in the field of mechanical testing. Clearly, collision and sweep embodiments may be implemented on the same basic frame.
3.2 Collision Embodiment of Impact Tester 3.2.1 Introduction As mentioned above, in the collision embodiment, the UHIT is a two-car compression specimen impact tester. It differs substantially from the methods currently utilized in that no foundation work is required to support the frame of the impact tester, and in that the initial potential energy is delivered to the specimen net of minor and well circumscribed energy losses. Details of two particular implementations are given below.
3.3.2 Physical Simulation of Cold Heading Process Cold heading is a cold forging process in which the force developed by a heading tool is employed to displace metal to form a section of different contour or of a different cross section. 1'he process is widely used to produce a variety of small and medium sized hardware items, for example bolts, nuts and rivets.
Although rules of thumb are still used in industry to successfully produce cold-headed parts, the imperatives of competitiveness are bringing cold headers to employ physical and mathematical simulations of the process to arrive at optimal forging sequences.
Mathematical simulations using, for example, Finite Element Methods, require inputs such as data on friction between die and work piece, fracture criteria constants, and flow stress relationships to be applied successfully. It is an objective of my invention to offer cold headers a means of rapidly and accurately generating these pieces of information.
The teachings of my invention can be readily understood by considering the following description in conjunction with the accompanying drawing, C, in which like numerals denote like parts throughout the two views.
Figure C 1 is a perspective view of two cars with dies.
Figure C2 is a vertical section through the die axes shown in Figure C 1 before collision.

Figure C3 is a vertical section through the die axes shown in Figure C 1 after collision.
In accordance with my invention, a cold heading specimen ( 1 ) is mounted in die cavity (12). Cars (3) and (4) are raised to the desired height at the ends of oppositely inclined track segments, and latched in the armed position. The cars are released, and move down the inclined segments of the track, propelled by gravity. During the collision event that occurs in the middle of the horizontal track segment, the kinetic energy of the cars is dissipated into the specimen. The specimen takes on the appearance, Figure C3, of a mushroom (1 a). The specimen generally falls out of the dies following recoil of the cars, and can be conveniently funneled into a calorimeter to ascertain the total absorbed energy. The metallographic analysis of the specimen yields valuable information for input into the FEM model.
3.2.3 Modelling of Material Flow Stress The Compression Test is the preferred method for determining flow stress data for materials at various temperatures, strains and strain rates. It is especially useful in view of its inherent capability for applying large strains, such as those experienced in most bulk metal forming processes. Other tests used for determining flow stress are the tensile test and the torsion test. Tensile tests are of limited use in bulk metal forming processes, because the results are valid only for relatively small amounts of plastic strains. The torsion test is typically used for finding flow stress data at higher true strains between 2 and 4, but the deformation is by definition non-homogeneous. Various types of machines can be used to perform a compression test. The Hydraulic Press can keep the strain rate constant by controlling the speed versus stroke of the press ram such that ram-velocity is a constant. In the Mechanical Press, with its regular crank or eccentric cam, the strain rate is not constant during the press stroke. Therefore average values of strain rate must be used. The latter two machines generally have a lower strain rate capability, and not within the range experienced in cold forging applications, for example. The Cam Plastometer is the classical method of determining the flow stress. Here, a specimen is fixedly held. A rarn rapidly and controllably strikes the specimen with a given stroke distance to deform the specimen. A hydraulic motor and a flywheel rotate a cam; in turn, a cam follower governs the motion of the ram. The cam is specifically configured to drive the ram at a constant strain rate. The main drawback with this machine is the compliance or bedding-in of the drive train components. The application of correction factors throws doubt on the validity of the data.
In its collision embodiment, the Universal Horizontal Impact Tester can be used to obtain material flow stress data and to establish constitutive models of material flow stress. The procedure is straightforward. A finely polished platen is inserted into the die pocket of each car, and a cylindrical specimen is lightly attached to the platen of one car by means of paraffin or similar lubricant. Those practiced in the art of mechanical testing know that the specimen must be upset without barreling to maintain a state of uniform stress.

Barreling can be prevented or at least minimized by employing several techniques, two of which are described below.
In one technique, maintaining adequate lubrication between the polished platens and the specimen during the compression event minimizes barreling. In this case, two types of cylindrical specimens are generally used to maintain the lubricant in place:
A. Spiral groove specimens: spiral grooves machined at both ends to a depth of about 0.25 mm are filled with lubricant.
B. Rastagaev specimens: recesses machined at both ends are filled with lubricant.
The grooves or recesses provide nearly frictionless and uniform metal flow.
For both types of specimens, the preferred height to diameter ratio is 1.5 to 1. The maximum specimen diameter is based on testing machine capacity.
Siebel and Pomp [5] developed another technique. They suggested that a uniform distribution of stress be obtained by compressing the cylindrical test specimen, not between two plane platens, but between two cones. The generatrices of these cones make an angle with the plane of compression, equal to the angle of friction. The resultant stress in the compression surfaces of the two cones is then parallel to the direction of compression. This favors the development of a pure axial compressive stress in the test specimen.
Both techniques can be readily implemented using my horizontal impact tester operating in the collision mode.
The two cars are released simultaneously. During the ensuing collision event, an accelerometer attached to one of the cars is used to obtain the deceleration as a function of time. The force history, F(t), is obtained by multiplying the deceleration a(t) by the total mass of the cars, and the specimen, M, according to the well-known law of Newtonian physics:
F(t) = M a(t) After obtaining the force history, the above equation can be integrated with respect to time to obtain the velocity history:
1 /M j F(t)dt = j dv from t = 0 to t = t in the LHS of the equation, and from v = vo to v = v in the RHS of the equation.
After obtaining the velocity history, the velocity can then be integrated with respect to time to obtain the deformation history, L(t):

j V(t)dt = j dL
from v = vv to v = v in the LHS of the equation, and from L = Lo to L = L in the RHS of the equation.
The area of the compression specimen as a function of time, A(t), is known since the deformation is essentially homogeneous, and A(t) = VS L(t), by virtue of the well known fact that the volume of the specimen, VS, is essentially constant during plastic deformation. Therefore, the flow stress of the material, a (t), can be calculated as:
a (t) = F(t) / VS L(t) The strain can now be calculated from the definition of true strain:
E(t) = In (Lo/L(t)) while the strain rate, slot, can be calculated from its defining equation:
sdot(t) = ds(t) /dt Thus, the three quantities essential in constitutive modelling of flow stress, namely, a (t), s(t), and sdot(t) are established as a function of a common parameter, t, enabling 6 to be plotted or curve fitted as a function of s and Edot.
An additional extremely important parameter in the establishment of flow stress, namely the temperature history of the specimen, can be determined using my horizontal impact tester. Indeed, my tester exploits the slight rebound after the impact to release the compression specimen from the grip of the platens. The specimen then drops and funnels into a calorimeter, located between the tracks. The final heat content of the specimen may be ascertained using the simple and well-known thermodynamic relation:
Q=mCpOT
where Q is the heat content of the specimen determined by the calorimeter, m is the mass of the specimen, Cp is the heat capacity of the test material, and DT is the temperature elevation above ambient temperature, Tambient. Here, OT = Tfn~ - Ta,,,bient The final specimen temperature, Tfn~,, can thus be easily calculated. Since the heat is rapidly developed in the specimen, the compression is essentially adiabatic, with little loss to the platens. The value of Q therefore approximates the energy input to the specimen. This enables the implementation of a Finite Element Model operating in the thermally-coupled adiabatic mode, and the derivation of a fit between the values of 6 (t), s(t) and Edot(t) and Tfnal by successive iterations, thereby generating the temperature history of the specimen, T(t).

Although it is realized that the flow stress surface is not a state variable, i.e., is not strictly independent of the path, the information generated by this technique implemented with the aid of my horizontal impact tester is nevertheless invaluable in the development of bulk metal forming processes.
The teachings of my invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawing, D, in which like numerals denote like parts throughout the two views.
Figure D 1 is a perspective view of two cars with smooth platens.
Figure D2 is a vertical section through the specimen axis shown in Figure D1 before collision.
Figure D3 is a vertical section through the specimen axis shown in Figure D 1 after collision.
In accordance with my invention, a Plastometer specimen ( 1 ) is axed to the platen ( 10) of one of the two cars (3) and (4) using, for example, paraffin(17). The cars are initially latched in the armed position at a desired height at the ends of oppositely inclined track segments. The cars are released, and move down the inclined segments of the track, propelled by gravity. During the collision event that occurs in the middle of the horizontal track segment, the kinetic energy of the cars is dissipated into the specimen through the platens. The specimen then falls into a funnel (13), and thence into a calorimeter (14). The metallographic analysis of the specimen yields valuable information for input into the FEM model. Also the data collected by the accelerometer is converted, as mentioned in Section 3.2.3, into information on the stress, strain, strain rate relation required for the Finite Element Method cold heading simulation.
3.3 Sweep Embodiment of Impact Tester 3.3.1 Introduction As mentioned above, in the sweep embodiment, the UHIT is a two-car fracture specimen impact tester. It differs substantially from the methods currently utilized in that no foundation work is required to support the frame of the impact tester, and in that the initial potential energy is delivered to the specimen net of minor and well circumscribed energy losses. Details of five particular implementations are given below.
3.3.2 Charpy Specimen Impact Energy Determination In the Charpy test, a weight carried on a pendulum swings down from a raised position to strike the middle of a test-sample which is supported at either end, the striking taking place at the bottom or "six o'clock" position in the movement of the pendulum.
The energy potentially available in the pendulum in the initial raised position is determined by its height above the strike location, and whatever energy remains in the pendulum after fracturing the test-sample will cause the pendulum to swing further and rise along an arc that can be measured. The maximum height to which the weight rises after fracturing the test-sample is proportional to the energy remaining in the weight after the fracture of the test-sample, and the difference between this and the initial energy is that which is absorbed by the sample during fracture.
The Charily test and procedures similar to it, including ones carried out on Charily Standard, Charily Sub-Size, and Charily V-Notch specimens, are limited to relatively low fracture energies and have further disadvantages related to the space required to permit the weight/pendulum combination to swing freely. To accommodate larger energies, considerably larger pendulums would have to be built, but these are both costly and difficult to construct.
The teachings of my invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawing, Figure E, in which like numerals denote like parts throughout the several views.
Figure E1 is a perspective view of two cars mounted on their respective tracks.
Figure E2 is a front elevation view of Figure E1.
Figure E3 is a side elevation view of Figure E1.
Figure E4 is a top plan view of Figure E 1.
In accordance with my invention, a Charily specimen (1) is placed on in the upper car (4) riding on the outer track (6). The lower car (3) rides on track (5), and carries the tup (2).
The specimen is often provided with a V- notch, centrally located, the notch being machined. It will thus be seen that the fracturing load will be applied in the middle between the two support locations. This means that the fracturing impact will take place substantially opposite the V-notch, thus ensuring that a fracture will begin to propagate from the V-notch and will extend through to the other side to complete the fracturing of the test-piece.
Cars set at a desired height and loaded with the desired weights are released, and thence propelled by gravity towards their respective horizontal track segments where impact between the fracture specimen and the tup occurs. Following fracture, the cars sweep over to and up their respectively opposite inclines, and displace devices to mark the apogee of their travel on scales typically graduated in millimeters.
Alternatively, non-return clutches hold the cars in place until a reading on each scale can be ascertained.
The impact energy absorbed by the specimen is a function of the difference between initial and final heights of car centers of mass. By repeating the test with the specimen taped to the upper car such that no impact may occur, the cars are launched again, and as before, the heights of the car centers of mass are measured.

It is more practical to modify the initial impact energy by varying car height rather than car mass, although it is entirely possible to design cars of adjustable mass.
3.3.3 Izod Impact Energy Determination In the Izod test, a weight carned on a pendulum swings down from a raised position to strike a test specimen that is supported as a cantilever beam, i.e., at one end, the striking taking place at the bottom or "six o'clock" position in the movement of the pendulum.
The energy potentially available in the pendulum in the initial raised position is determined by its height above the strike location, and whatever energy remains in the pendulum after fracturing the test specimen will cause the pendulum to swing further and rise along an arc that can be measured. The maximum height to which the weight rises after fracturing the test specimen is proportional to the energy remaining in the weight after the fracture of the test specimen, and the difference between this and the initial energy is that which is absorbed by the sample during fracture.
The Izod test is thus similar to the Charpy test, differing only in the test specimen geometry and method of support. The Izod test is also limited to relatively low fracture energies. To accommodate larger energies, considerably larger pendulums would have to be built, but these are both costly and difficult to construct.
The teachings of my invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawing, F, in which like numerals denote like parts throughout the several views.
Figure F 1 is a perspective view of two cars mounted on their respective tracks.
Figure F2 is a front elevation view of Figure F 1.
Figure F3 is a side elevation view of Figure F1.
Figure F4 is a top plan view of Figure F 1.
In accordance with my invention, an Izod specimen ( 1 ) is mounted in holder ( 16) in the lower car (3) riding on inner track (5). The upper car (4), of mass substantially equal to that of the lower car, rides on the outer track (6). The cars are set at equal heights on the inclined track segments, released, and thence propelled by gravity towards the horizontal track segments. As the cars sweep by one another, the striker (2) of the upper car engages the Izod specimen in the holder of the lower car. The specimen normally sustains fracture, allowing the cars to sweep past one another, and to travel up the opposite inclined track segments. 'the energy expended in fracturing the specimen is calculated from the initial and final height of each car. The unrestrained portion of the specimen is normally thrown clear of the cars. It is more practical to modify the initial impact energy by varying car height rather than car mass, although it is entirely possible to design cars of adjustable mass.
3.3.4 Skelp Impact Energy Determination Fracture tests are used for other purposes than simply the determination of absorbed fracture energy. For example, much of the piping utilized for pipelines in the Arctic is manufactured by a helical seam-welding procedure, in which heavy steel plate, also known as skelp, with a thickness in the area of 12 mm to 25 mm is helically coiled and welded as the edges come together, to form large-diameter pipe capable of withstanding high internal pressures.
Because pipelines may experience ambient temperatures as low as - 40 Celsius, it is desirable to know the nature of a fracture occurring in this material in the low temperature range. It is known that the brittleness of certain steels increases as the temperature drops. Therefore it is of advantage to ensure that steel skelp of the kind proposed for use in Arctic pipelines will undergo ductile fracture to some extent. This reduces the risk that a crack in a portion of a highly pressurized pipeline in very cold conditions will run rapidly along the pipeline due to the inability of the skelp to absorb energy at those temperatures.
In order to determine the nature of the fracture for such material, it is known to prepare elongated test samples with a notch about the middle of one longitudinal edge, to cool the sample down to a desired stipulated temperature, for example -40 Celsius, to mount the sample between two supports such that the V-notch is downwardly, and then to drop a relatively heavy drop-weight vertically down to strike the sample at the edge opposite the V-notch, thereby causing a fracture to propagate from the underlying V-notch to the edge which has been struck. An examination of the fracture surfaces then allows the metallurgist to determine whether the sample has undergone ductile or brittle fracture.
Drop-weight towers can be instrumented to measure the deceleration of a drop-weight by attaching bonded wire strain gages or piezoelectric transducers to the striker bar or to suitably designed anvils. However, the attachment of shielded cables to the drop-weight would create maintenance problems. The resonant vibrations within the drop-weight or the anvils contribute unwanted signals during impact. Therefore, the latter approach is neither reliable nor accurate unless great expense and design effort is expended.
If only a few samples are to be tested, as during an investigation of material properties, the energy remaining in the drop weight is used to deform a cube of aluminium.
The change in the dimensions of the cube is correlated with the known energy required to cause that deformation. However, for repeated testing of a large number of samples, the use of aluminium cubes is impractical.
As stated previously, the total potential energy in the drop-weight available to be applied to a sample is determined by multiplying the weight of the drop-weight by the effective height of the drop-weight above the test-piece. After the drop-weight has struck and fractured the test-piece, some energy will remain in the drop-weight as kinetic energy. In other words, the drop-weight will be continuing to fall, and its speed at any given point when multiplied by it mass will give the instantaneous kinetic energy. The difference between these two energies (so long as both are referenced to the position of the test-piece) is a measure of the energy absorbed by the test-piece during fracture.
It is not practical for a number of reasons to actually measure the remaining kinetic energy in the drop-weight after fracture by catching and absorbing the energy in some deceleration device like a shock absorber. What is contemplated here is to catch and decelerate a drop-weight with a mass of 1200 pounds falling from 12 feet, even after some of that energy has been absorbed in the fracture of the test-piece. The strain placed on the device utilized to catch and decelerate the drop-weight is very considerable, and a proposal to utilize that particular device as a sensitive instrument to determine the energy thus absorbed would immediately encounter problems of wear, distortion, shock absorber oil leakage, and simple fracture of the loaded portions.
U.S. Pat. No 4,085,609 issued to J.H. Kelly purports to provide a superior method of determining loss of energy by the drop-weight during impact. One aspect of this invention is to obviate the difficulties and drawbacks with the use of strain gages or piezoelectric transducers. His invention provides apparatus for determining the energy absorbed by an elongated test-piece of material during fracture. It comprises support means for the test-piece during fracture including anvil means at either end of the test-piece; a drop-weight, vertical guide means for the drop-weight, means for raising the drop weight along the guide means, and means for releasing the drop weight from a raised position directly above the test-piece to undergo substantial free-fall vertically after release. The means for measuring the motion of the drop weight after the test-piece has been fractured include two retro-reflective areas affixed in vertically separated relation on the drop weight, a photoelectric beam projecting such that the retro-reflective areas pass sequentially into the beam, light-detecting means for sensing light reflected from the areas and for generating two time-separated electrical signals as the two areas pass sequentially into the beam, and electronic period-counter means to measure the time elapsing between the two electrical signals. The drop weight is an integral mass of metal shaped to define two downwardly extending, laterally spaced-apart arms joined integrally together at the top. These provide an internal slot extending upward from the bottom, the guide means maintaining the drop weight in an orientation such that the test-piece is aligned with the internal slot, the drop weight including a striker bar supported horizontally across and at right-angles to the slot and said test-piece. The striker bar contacts the test-piece substantially mid-way of each so that the fractured separated ends of the test-piece can pivot inwardly and into the slot above the striker bar.
This avoids interference with the further downward free-fall of the drop weight. Means directly beneath the initial test-piece location provide for catching and decelerating the drop weight after fracture of the test-piece.
However, the need for, and cost associated with, a very large foundation remains.
Moreover, sophisticated electronic means are required for determining the energy absorbed by the skelp specimen.
In contradistinction, my apparatus advantageously overcomes the deficiencies associated with this materials testing system.

The teachings of my invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawing, Figure G, in which like numerals denote like parts throughout the several views.
Figure G1 is a perspective view of two cars mounted on their respective tracks.
Figure G2 is a front elevation view of the two cars of Figure G1.
Figure G3 is a side elevation view of the two cars of Figure G1.
Figure G4 is a top plan view of the two cars and tracks of Figure Gl .
In accordance with my invention, a large-size skelp V-notch specimen (1) is placed in recess (15) in the upper car (4) riding on the outer track (6). The lower car (3) rides on track (5), and carries the tup (2). As well known to those practiced in the art of impact testing, the specimen includes two end portions, a central waist, and transition radii. The specimen is typically machined from a piece of steel skelp, and thus is relatively narrow and elongated. As illustrated in Figure G2, the specimen is positioned such that the original plane of the skelp from which the specimen is machined lies flat in the recess.
The specimen is provided with a V-notch, centrally located, the notch being machined or impact-impressed. It will thus be seen that the fracturing load will be applied in the middle between the two support locations. This means that the fracturing impact will take place substantially opposite the V-notch, thus ensuring that a fracture will begin to propagate from the V-notch and will extend through to the other side to complete the fracturing of the specimen.
Cars set at a desired height and loaded with the desired weights are released, and thence propelled by gravity towards their respective horizontal track segments where impact between the fracture specimen and the tup occurs. Following fracture, the cars sweep over to and up their respectively opposite inclines, and displace devices to mark the apogee of their travel on scales typically graduated in millimeters.
Alternatively, non-return clutches hold the cars in place until a reading on each scale can be ascertained.
The impact energy absorbed by the skelp specimen is a function of the difference between initial and final heights of car centers of mass. By repeating the test with the specimen taped to the upper car such that no impact may occur, the cars are launched again, and as before, the heights of the car centers of mass are measured.
It is more practical to modify the initial impact energy by varying car height rather than car mass, although it is entirely possible to design cars of adjustable mass.

3.3.5 Bolt Head Decapitation Energy Determination During the manufacture of bolts by the cold heading process operators periodically check the soundness of the juncture between head and shaft by conducting a dynamic wedge test. This consists of mounting a bolt specimen in a specially designed jig, placing a wedge between the anvil of the jig and the underside of the bolt head, and manually applying a blow with a hammer of specified mass, in an attempt to remove the bolt head from the bolt shaft, i.e., decapitate the bolt. This test is a go-no go, or pass-fail test. It gives no information as to the energy absorbed by the bolt, i.e., the decapitation energy.
The particular embodiment of my invention described in this section can be used to ascertain precisely the decapitation energy. Knowledge of this energy is invaluable to rapidly apply corrective measures in the manufacturing process.
The teachings of this particular implementation of my invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawing, Figure H, in which like numerals denote like parts throughout the several views.
Figure H1 is a perspective view of two cars riding on their respective tracks.
Figure H2 is a front elevation view of Figure H1.
Figure H3 is a side elevation view of Figure H 1.
Figure H4 is a top plan view of Figure H1.
In accordance with my invention, a bolt specimen (1) is placed in the specially designed holder (16) in lower car (3) riding on track (5), and is tightened against striker plate (2).
The upper car (4), of mass substantially equal to that of the lower car, rides on the outer track (6). The cars set at equal heights are released, and thence propelled by gravity towards the horizontal track segments. As the cars sweep by one another, the upper car engages the striker plate of the lower car, imparting decapitation energy to the bolt specimen. The bolt head is normally separated from the shaft of the bolt by the impact, allowing the cars to sweep past one another, and travel up the opposite inclined track segments. The decapitation energy expended in separating the bolt head from the bolt shaft is a function of the sum of the differences between initial and final heights of the mass centers of the cars. The bolt head is normally thrown clear of the cars.
It is more practical to modify the initial impact energy by varying car height rather than car mass, although it is entirely possible to design cars of adjustable mass.

3.3.6 Tensile Impact Energy Determination Conventional tensile testing machines generally operate at low strain rates, that is, at strain rates of the order of 10'3 sec'1. Exceptionally, some machines can be operated at100 sec 1. It is sometimes useful to conduct tensile tests at rates which can be construed as impact testing rates, since flow stress phenomena differ considerably from those observed at low strain rates.
The Universal Horizontal Impact Tester can perform dynamic tensile tests in much the same way as it is used in decapitating bolts, the difference residing in the configuration of the test specimen.
The teachings of my invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawing, Figure I, in which like numerals denote like parts throughout the several views.
Figure I1 is a perspective view of two cars mounted on their respective tracks.
Figure I2 is a front elevation view of Figure I l .
Figure I3 is lateral elevation view of Figure I1.
Figure I4 is a plan view of Figure I1.
In accordance with my invention, a tensile specimen (1) is placed in the specially designed specimen holder (16) in lower car (3) riding on track (5), and is bottomed in the specimen holder. The striker plate (2) is positioned against the nut. The upper car (4), of mass substantially equal to that of the lower car, rides on the outer track (6). The cars set at equal heights are released, and thence propelled by gravity towards the horizontal track segments. As the cars sweep by one another, the upper car engages the striker plate of the lower car, imparting a dynamic tensile force to the tensile specimen.
The specimen normally necks down and fractures in the gauge portion of the specimen, allowing the cars to sweep past one another, and travel up the opposite inclined track segments. The tensile impact energy expended in elongating and fracturing the specimen is a function of the sum of the differences between initial and final heights of the mass centers of the cars. Alternatively, an accelerometer located on the upper car can be used to obtain the deceleration as a function of time. The relation between stress, strain, and strain rate can then be determined using the computational procedure outlined in Section 3.2.3.
It is more practical to modify the initial impact energy by varying car height rather than car mass, although it is entirely possible to design cars of adjustable mass.

Claims

Claims What I claim as novel, useful and inventive, and desire to secure by Letters Patent is:
A Universal Horizontal Impact Tester that is:

a multi-purpose apparatus for horizontally delivering a well-defined quantity of mechanical energy to a compression specimen, and determining the amount of energy absorbed by the specimen, while obviating the need for foundation work;
a multi-purpose apparatus for horizontally delivering a well-defined quantity of mechanical energy to a tensile specimen, and determining the amount of energy absorbed by the specimen, while obviating the need for foundation work;
a multi-purpose apparatus for horizontally delivering a well-defined quantity of mechanical energy to a fracture specimen, and determining the amount of energy absorbed by the specimen, while obviating the need for foundation work.