GB1604396A - Apparatus for measuring stress relaxation in elastomers - Google Patents
Apparatus for measuring stress relaxation in elastomers Download PDFInfo
- Publication number
- GB1604396A GB1604396A GB4346177A GB4346177A GB1604396A GB 1604396 A GB1604396 A GB 1604396A GB 4346177 A GB4346177 A GB 4346177A GB 4346177 A GB4346177 A GB 4346177A GB 1604396 A GB1604396 A GB 1604396A
- Authority
- GB
- United Kingdom
- Prior art keywords
- contact
- platen assembly
- platen
- jig
- break
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 229920001971 elastomer Polymers 0.000 title description 13
- 239000000806 elastomer Substances 0.000 title description 12
- 238000012360 testing method Methods 0.000 claims description 35
- 238000007906 compression Methods 0.000 claims description 19
- 230000006835 compression Effects 0.000 claims description 17
- 238000005259 measurement Methods 0.000 claims description 13
- 230000000712 assembly Effects 0.000 claims description 10
- 238000000429 assembly Methods 0.000 claims description 10
- 238000006073 displacement reaction Methods 0.000 claims description 8
- 239000000463 material Substances 0.000 claims description 8
- 230000007246 mechanism Effects 0.000 claims description 7
- 239000000725 suspension Substances 0.000 claims description 4
- 238000012806 monitoring device Methods 0.000 claims description 3
- 238000001514 detection method Methods 0.000 claims description 2
- 230000007257 malfunction Effects 0.000 claims description 2
- 230000035945 sensitivity Effects 0.000 claims description 2
- 238000012956 testing procedure Methods 0.000 claims description 2
- 125000006850 spacer group Chemical group 0.000 description 7
- 229910000639 Spring steel Inorganic materials 0.000 description 4
- 230000002093 peripheral effect Effects 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 239000012212 insulator Substances 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 238000007789 sealing Methods 0.000 description 2
- 101100058320 Arabidopsis thaliana BHLH12 gene Proteins 0.000 description 1
- 230000004323 axial length Effects 0.000 description 1
- 238000012668 chain scission Methods 0.000 description 1
- 238000004132 cross linking Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 239000012777 electrically insulating material Substances 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- UONOETXJSWQNOL-UHFFFAOYSA-N tungsten carbide Chemical compound [W+]#[C-] UONOETXJSWQNOL-UHFFFAOYSA-N 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
- G01N3/10—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces generated by pneumatic or hydraulic pressure
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/44—Resins; Plastics; Rubber; Leather
- G01N33/445—Rubber
Landscapes
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Engineering & Computer Science (AREA)
- Food Science & Technology (AREA)
- Medicinal Chemistry (AREA)
- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
Description
(54) APPARATUS FOR MEASURING STRESS RELAXATION IN
ELASTOMERS
(71) We, RUBBER AND PLASTICS RE- SEARCH ASSOCIATION OF GREAT BRITAIN, a
British company, of Shawbury, Shrewsbury,
Salop, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention is concerned with the measuring of stress relaxation in elastomers.
Many applications of elastomers make use of the ability of such materials, when under compression, to fill a gap between the surfaces of two rigid components, often to prevent the passage of a fluid through the gap. These applications fall into two categories: (i) where the surfaces are able to move relative to one another and apply a stress to the elastomer, and (ii) where the relative positions of the rigid components are fixed and the force between these components and the elastomer is determined solely by the elastomer.
In the majority of such applications, the elastomeric component is required to perform long-term service and to operate in a detrimental environment (thermal and/or chemical), and so the determination of the properties of the elastomer under realistic service conditions is most important. Of primary importance in sealing applications is the stress at the interfaces between the elastomer and the rigid components, since this governs the working pressure in the sealed system. Where the relative positions of the rigid components are fixed. the strain in the elastomer is fixed and the stress is variable, then the measurement of stress relaxation provides the most realistic test procedure.
The sealing stress is a function of the strain applied to the elastomer, the geometry of the seal and the modulus of the elastomer. Since the strain and geometry are constant, the stress is dependent upon the modulus. Thus, a knowledge of how the modulus varies with time under operating conditions allows seals to be designed for a required operating life.
Measurement of stress relaxation, see for example our previous U.K. Patent Specification No. 1 529223, provides a means for measuring the decrease in modulus with time. This decrease in modulus is caused by two mechanisms: (i) physical, due to the viscoelastic nature of elastomeric materials, and (ii) chemical, due to chain scission, further crosslinking, etc. The chemical mechanism predominates at high temperatures over long periods of time. Because of the varying contributions of the two types of mechanism to the decrease in modulus, it is not safe to use tests at higher temperatures over shorter times to obtain information with respect to the properties of elastomeric materials over longer times at lower temperatures.
Because of the lengthy time scale of test periods and the number of individual tests required, the provision for testing a number of samples at any one time is most desirable.
This makes the cost of the test apparatus of great importance. In this connection, it is known to use a jig mechanism to impose the strain on the specimen, this jig mechanism being separate from the stress measuring system, of which only one such system is then required. In order to accomplish this, one of two plates applying a compressive stress to the test specimen or sample is allowed to move in the direction of compression. The force required to move this plate by a very small additional amount in the direction of compression is then measured. This force comprises three components: (i) the force exerted by the sample in its normally compressed state (i.e. before measurement), (ii) the force exerted by the sample due to slight over-compression during measurement, and (iii) any forces produced by the jig, e.g.
through friction. As the first component is the one of interest, the second and third must either be very small compared with the first or be accurately known. It is because of this requirement that jigs and stress measuring equipment must conform to certain specifications.
In accordance with the present invention, an apparatus for use in the measurement of stress relaxation of elastomeric materials comprises a pair of platen assemblies having respective platens disposed at a predeter mined distance apart for applying a test compression to a test sample disposed therebetween, and hydraulic power cylinder means for temporarily displacing one of the platen assemblies in a direction towards the other to reduce said predetermined distance and thereby subject the sample to an additional test compression, said one platen assembly being supported displaceably on a fixed member by means of a spring diaphragm suspension which includes a pair of parallel annular spring diaphragms whose inner edges are rigidly connected to a part of said one platen assembly extending into a bore in said fixed member and whose outer edges are rigidly connected to said fixed member so as to support said one platen assembly coaxially within the bore, said displacement of the one platen assembly towards the other being arranged to break an electrical connection between non-movable and movable parts carried by said fixed member and said one platen assembly respectively, and further comprising a monitoring device for detecting said break in the electrical connection and a load cell device for detecting the force applied by said hydraulic power cylinder means to said one platen assembly to achieve said break.
In some embodiments, the spring suspension can include more than two spring diaphragms if desired but two is normally the optimum number to achieve the required displacement of said one platen assembly towards the other while constraining said one platen assembly against movement in other directions or modes.
Advantageously, said other platen assembly comprises an insert of adjustable length which extends slidably into a bore in a further fixed member, the extent of projection of the insert into the latter bore being fixed by a screw plate received in an increased diameter end portion of the bore to enable said predetermined distance and hence the initial compression of the sample to be predetermined by the length of the insert.
To facilitate the measurement of stress relaxation in a plurality of elastomeric samples, the apparatus can include a corresponding plurality of pairs of said platen assemblies. Conveniently, the latter can be mounted on a rotatable turntable to enable each sample to be brought sequentially to a single stress measuring station where said force detection is made.
The invention is described further hereinafter, by way of example, with reference to the accompanying drawings, in which:
Fig. 1 is a diagrammatic side elevation of one embodiment of an apparatus in accordance with the present invention;
Fig. 2 is a sectional side elevation of part of the apparatus of Fig. 1 on the line Il-Il of
Fig. I;
Fig. 3 is a block circuit diagram of a control arrangement of the apparatus of Fig.
I; Fig. 4 is a circuit diagram of one embodiment of a contact break sensor;
Fig. 5 illustrates the control circuitry for the hydraulic actuating cylinder;
Fig. 6 is a plan view of an apparatus designed to hold a plurality of samples; and
Fig. 7 is a partial section on the line A-A of Fig. 6.
Fig. I is an overall view showing ajig 10 in its operative position prior to making a test measurement on an elastomeric sample or specimen 12. The principal parts of the jig are shown in more detail in Fig. 2. With reference to the latter figure, the jig comprises a pair of parallel beams 14, 16 which are held apart in fixed spatial relationship by two or more rigid spacer members 18 (not shown in Figure 2, but see Fig. 1). The beams 14 and 16 carry upper and lower platens 20 and 22, respectively, for receiving an elastomeric sample 12 under test therebetween, the lower platen 22 being arranged to be effectively fixed in relation to the lower beam 16 but the upper platen 20 being mounted on the upper beam 14 so as to be capable of limited displacement relative thereto in a direction perpendicular to the working surface 24 of the lower platen 22.For the latter purpose, the upper platen 20 forms part of a rigid platen assembly 26 which extends into a transverse bore 27 in the upper beam 14 and is connected thereto by a pair of annular spring steel diaphragms 28, 30 which permit a limited displacement of the assembly 26 in its axial direction but restrict any transverse or angular displacement relative to the beam bore 27.
In addition to the platen 20, the assembly 26 comprises a bolt-like member 32 having a head portion 34 and a screw-threaded shank 36 which is received in a correspondingly screw-threaded blind bore 38 in the platen 20. Clamped between the head of the member 32 and the upper surface of the platen 20 are a pair of annular bushes 40, 42 of electrically insulating material and a metallic annular spacer member 44 whose inner diameter is such that it does not contact the shank 36 of the member 32. The inner peripheral portions of the spring steel diaphragms 28, 30 are firmly clamped between the insulator 42 and the spacer 44 and between the insulator 42 and the spacer 40, respectively.
The bore 27 in the upper beam 14 contains a portion 46 of increased diameter which receives a further annular spacer 48, of identical axial length to the spacer 44, which firmly clamps the outer peripheral portion of the spring steel diaphragm 28 against the shoulder 50 formed between the bore por tions 27 and 46. The outer peripheral portion of the other spring steel diaphragm is clamped between the spacer 48 and a reduced diameter portion 51 on the free end of a generally u-shaped member 52 which is rigidly connected to the upper beam 14 by bolts (not shown).
The upper end of the head of the bolt-like member 32 is radiussed and is engageable by the flat lower end surface of a screw-threaded bore 56 in the base of the member 52. the latter bore 56 being axially aligned with the shank 36. A lock-nut 58 enables the axial projection of the rod 54 into the member 52 to be pre-set. For a purpose explained further below, the bolt-like member 32 carries a pin 60 which projects transversely from either side of the member 32 as shown in Fig. 1.
The lower platen 22 is formed by the closed end of a cup-shaped member 62 which is slidably received with minimum clearance in a transverse bore 64 in the lower beam 16.
The internal wall 66 of the member 62 is screw-threaded and receives a correspondingly screw-threaded cylindrical insert 68 having an axial screw-threaded through-bore 70 which itself receives a set screw 72. The assembly comprising the members 62, 68 and 72 is held in place by a circular plate 74 having a screw-theaded periphery 76 which is received in a correspondingly screwthreaded increased diameter portion 78 of the bore 64. Thus, as described further below, once the relative positions of the members 62 and 68 have been set by the set screw 72 and the plae 74 is screwed fully home against the shoulder 80 between the bore portions 64 and 78, the position of the working surface 24 of the lower platen 22 is set relative to the upper beam 14 and hence relative to the upper platen 20.
In use, the sample 12 under test is positioned between the platens 20, 22 and subjected over a period of time to a predetermined test compression. Stress relaxation is monitored by periodically subjecting the sample to an additional small over-compression, the force required to achieve this additional compression being measured to provide information as to the stress relaxation in the sample. The procedure for sensing this small amount of movement is to detect the break or opening of an electrical contact between fixed and moving parts of the jig.
Conveniently, the electrical contact is between the rod 54 and the radiussed end of the bolt-like member 32.
It is apparent that in this jig, a force from the compressed sample 12 is transmitted through the contact. Therefore, because of the high levels of force which can be involved, the contact must be made from a material sufficiently hard to avoid deformation of the contact faces. The present jig employs, for example, either EN58 stainless steel or tungsten carbide, the radiussed contact face providing a well defined point of contact.
The insert of preset height, formed by the members 62, 68 and 72, and the threaded retaining plate 74 enable the sample to be loaded into the jig within a period laid down for tests of this kind (e.g. 30 seconds). Before loading, the insert height is calculated from the jig dimensions and the desired percentage compression, and is set using a micrometer gauge. The jig is then inverted, the sample 12 placed on the upper platen 20, the insert located in the bore 64, the retaining plate screwed fully home against the shoulder 80 and the jig returned to its normal orientation.
To conduct a test, the force necessary to break the above-described electrical contact, and hence achieve the additional test compression, is measured by the stress measuring system, now to be described, which moves the upper platen assembly downwards by engagement with the pin 60. Because of the very small amount of movement necessary to achieve this additional compression, its contribution to the measured force may be neglected.
The basic mechanical components of the stress measuring system are shown diagrammatically in Fig. 1. The jig is held in a frame 86 beneath a hydraulic cylinder 88 whose piston rod 89 acts on the pin 60 of the jig via a load cell 90 and an electrically insulated bifurcated member 92, the longitudinal axis of the piston rod 89 being aligned with the axis of the jig so as to exert a uniform force on the upper platen assembly. The load cell (for example having a zero to 2kN range) is preferably of the resistance strain gauge type.
The control system for the stress measuring apparatus is shown diagrammatically in
Fig. 3. The jig contacts are indicated by the references A and B in Fig. 3 and are connected to a contact break sensor 98 which is illustrated in more detail in Fig. 4. The output of the sensor 98 is connected to a logic control circuit 100 which controls the operation of a solenoid valve 102 via a driver 104.
The output of the load cell 90 is connected via an amplifier 106 to a digital readout force indicator 108 and to an alarm sensor 110 having an associated visual and/or audible alarm indicator 112. The aforegoing system is adapted to perform the measurement of force with a minimum of operator involvement.
The solenoid valve 102 controls and is part of a hydropneumatic circuit which is illustrated in more detail in Fig. 5. The hydropneumatic circuit includes the hydraulic cylinder 88 which is of the low pressure type and whose speed is controlled by two flow valves 114, 116. Movement of oil within the circuit is effected by compressed air acting through two oil/air reservoirs 118, 120.
Directional control is achieved by the solenoid valve 102 which in this embodiment is of the four way type.
The circuit of the contact break sensor is shown in Fig. 4. Contact A is provided by the bolt-like member 32 of the upper platen assembly and contact B is formed by the body of the jig (rod 54). The contacts A and
B, together with a resistor R1 form one arm of a Wheatstone bridge.A resistor R2 limits the current flow through the contact and resistor
R, prevents an excessive rise in the voltage when the contact opens. A variable resistor
RV, enables the sensitivity of the circuit to be adjusted. An operational amplifier 122 acts as a comparator, providing a step change in output at a predetermined level of contact resistance, the step output thus obtained being fed to the logic control circuit 100.
In use, the aforegoing system functions as follows. Depression of a start button 124 activates the solenoid valve 102 to cause the piston rod of the cylinder 88 to move downwards whereby the end piece 92 on the load cell 90 eventually engages the pin 60 of the upper platen assembly of the jig, this engagement being arranged to complete the circuit of the contact sensor. The control circuit is arranged to sense this initial completion of the circuit and to then ignore any breaking of the circuit for a pre-set period to discriminate against contact bounce at the junction of the member 92 with the pin 60.
After this preset period, any opening of the contacts A, B triggers the control circuit which is arranged to immediately lock in and hold the prevailing force reading on the indicator 108 and to reverse the motion of the cylinder. In this way, the indicator automatically provides a reading corresponding to the force necessary to achieve the additional test compression of the sample as determined by the disengagement of the contacts A, B or by the resistance between the contacts A, B being increased to a predetermined level.
Prior to use of the apparatus and before loading with the specimen 12, the screwthreaded rod 54 and lock-nut 58 forming the fixed contact are adjusted so that light finger pressure on the upper platen assembly will break the contact. The jig is then placed in the stress measuring apparatus and the force necessary to break the contact is recorded.
The jig is then loaded with the test specimen 12 as described above and at the appropriate time after loading the force then necessary to break the contact is measured. The force exerted by the sample is obtained by subtracting the first measurement from the second.
An emergency return mechanism is provided for use by the operator in the event that the system malfunctions, a control being incorporated to reverse the piston and sound the alarm 112 should the force exceed a preset level.
In accordance with Fig. 1, each jig 10 can be adapted to hold a single test sample, the jig being inserted into the frame 86 whenever a test is to be made. Alternatively, the jig can be adapted to hold a plurality of samples as illustrated in Figs. 6 and 7 where the beams 14 and 16 are circular or annular plates having a plurality of platen arrangements of the type shown in Fig. 2 disposed in a ring.
The beams 14, 16 can then form a rotatable turret type arrangement which can sequentially bring each pair of platens and the associated sample under a single hydraulic cylinder 88 and load cell 90. In this way the testing of a large number of samples is facilitated. The latter operation can be readily automated so as to reduce still further the necessity for operator involvement in the testing procedure.
WHAT WE CLAIM IS:
1. An apparatus for use in the measurement of stress relaxation of elastomeric materials, comprising a pair of platen assemblies having respective platens disposed at a predetermined distance apart for applying a test compression to a test sample disposed therebetween, and hydraulic power cylinder means for temporarily displacing one of the platen assemblies in a direction towards the other to reduce said predetermined distance and thereby subject the sample to an additional test compression, said one platen assembly being supported displaceably on a fixed member by means of a spring diaphragm suspension which includes a pair of parallel annular spring diaphragms whose inner edges are rigidly connected to a part of said one platen assembly extending into a bore in said fixed member and those outer edges are rigidly connected to said fixed member so as to support said one platen assembly coaxially within the bore, said displacement of the one platen assembly towards the other being arranged to break an electrical connection between non-movable and movable parts carried by said fixed member and said one platen assembly respectively, and further comprising a monitoring device for detecting said break in the electrical connection and a load cell device for detecting the force applied by said hydraulic power cylinder means to said one platen assembly to achieve said break.
2. An apparatus as claimed in claim 1 wherein said non-movable and movable parts making said electrical connection are axially aligned with said bore, and wherein the position of the operationally non-movable part is pre-adjustable to enable the latter member to be brought into abutment with said movable member during setting-up of the apparatus.
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (9)
1. An apparatus for use in the measurement of stress relaxation of elastomeric materials, comprising a pair of platen assemblies having respective platens disposed at a predetermined distance apart for applying a test compression to a test sample disposed therebetween, and hydraulic power cylinder means for temporarily displacing one of the platen assemblies in a direction towards the other to reduce said predetermined distance and thereby subject the sample to an additional test compression, said one platen assembly being supported displaceably on a fixed member by means of a spring diaphragm suspension which includes a pair of parallel annular spring diaphragms whose inner edges are rigidly connected to a part of said one platen assembly extending into a bore in said fixed member and those outer edges are rigidly connected to said fixed member so as to support said one platen assembly coaxially within the bore, said displacement of the one platen assembly towards the other being arranged to break an electrical connection between non-movable and movable parts carried by said fixed member and said one platen assembly respectively, and further comprising a monitoring device for detecting said break in the electrical connection and a load cell device for detecting the force applied by said hydraulic power cylinder means to said one platen assembly to achieve said break.
2. An apparatus as claimed in claim 1 wherein said non-movable and movable parts making said electrical connection are axially aligned with said bore, and wherein the position of the operationally non-movable part is pre-adjustable to enable the latter member to be brought into abutment with said movable member during setting-up of the apparatus.
3. An apparatus as claimed in claim 2
wherein said movable part comprises a boltlike member forming part of said one platen assembly and having a radiussed end which makes said electrical connection with a flat surface on said non-movable part.
4. An apparatus as claimed in claim 3 wherein said bolt-like member carries a pair of laterally projecting pins engageable by said hydraulic power cylinder means for effecting said displacement of said one platen assembly.
5. An apparatus as claimed in any of claims 1 to 4 wherein the platens of said platen assemblies have parallel working surfaces between which the test sample is compressed.
6. An apparatus as claimed in any preceding claim wherein said other platen assembly comprises an insert of adjustable length which extends slid ably into a bore in a further fixed member, the extent of projection of the insert into the latter bore being fixed by a screw plate received in an increased diameter end portion of the bore.
7. An apparatus as claimed in any preceding claim which includes a plurality of pairs of said platen assemblies for receiving a corresponding plurality of elastomeric test samples.
8. An apparatus as claimed in claim 7 wherein the pairs of platen assemblies are mounted on a rotatable turntable to enable each test sample to be brought sequentially to a single stress measuring station where said force detection is made.
9. An apparatus for use in the measurement of stress relaxation of elastomeric materials substantially as hereinbefore described with reference to the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB4346177A GB1604396A (en) | 1978-05-25 | 1978-05-25 | Apparatus for measuring stress relaxation in elastomers |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB4346177A GB1604396A (en) | 1978-05-25 | 1978-05-25 | Apparatus for measuring stress relaxation in elastomers |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB1604396A true GB1604396A (en) | 1981-12-09 |
Family
ID=10428852
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB4346177A Expired GB1604396A (en) | 1978-05-25 | 1978-05-25 | Apparatus for measuring stress relaxation in elastomers |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB1604396A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112557212A (en) * | 2020-11-13 | 2021-03-26 | 广电计量检测（北京）有限公司 | Spring stress relaxation test device |
| CN112763339A (en) * | 2020-12-24 | 2021-05-07 | 中国兵器工业第五九研究所 | Online measurement method and system for elastic part load |
| CN116399679A (en) * | 2023-06-08 | 2023-07-07 | 深圳市鑫精诚传感技术有限公司 | Test pen and test device |
-
1978
- 1978-05-25 GB GB4346177A patent/GB1604396A/en not_active Expired
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112557212A (en) * | 2020-11-13 | 2021-03-26 | 广电计量检测（北京）有限公司 | Spring stress relaxation test device |
| CN112763339A (en) * | 2020-12-24 | 2021-05-07 | 中国兵器工业第五九研究所 | Online measurement method and system for elastic part load |
| CN112763339B (en) * | 2020-12-24 | 2023-07-25 | 中国兵器工业第五九研究所 | Online measuring method and system for load of elastic piece |
| CN116399679A (en) * | 2023-06-08 | 2023-07-07 | 深圳市鑫精诚传感技术有限公司 | Test pen and test device |
| CN116399679B (en) * | 2023-06-08 | 2023-08-01 | 深圳市鑫精诚传感技术有限公司 | Test pen and test device |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PS | Patent sealed | ||
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19930525 |