# US 10,481,057 B1 · Mechanical testing equipment for material characterization

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- Number: US 10,481,057 B1
- Document ID: US10481057B1
- Status: Granted
- Kind: B1
- Application number: 15/366,921
- Filed: 2016-12-01
- Granted: 2019-11-19
- Earliest claimed: 2016-12-01
- Assignees: National Technology & Engineering Solutions of Sandia, LLC
- Applicants: National Technology & Engineering Solutions of Sandia, LLC
- Inventors: Bo Song; Evan P. Johnson; Matthew A Spletzer; Jack D. Heister; Randy L. Everett; Thomas L. Martinez; Marlene E. Knight; Dennis John Kenney
- Web page: https://patentgrep.com/patent/US10481057B1

## CPC

- G01N 3/303: generated only by free-falling weight
- G01N 3/30: by applying a single impulsive force, e.g. by falling weight
- G01N 2203/0033: Weight
- G01N 2203/0075: Strain-stress relations or elastic constants
- G01N 2203/0098: Tests specified by its name, e.g. Charpy, Brinnel, Mullen
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

A mechanical testing apparatus for a specimen is presented. The mechanical testing apparatus comprises a drop table system and a Hopkinson bar. The drop table system has a drop carriage. The Hopkinson bar is positioned parallel to a motion of the drop carriage and connected to the drop table system by the specimen.

## Claims

### Claim 1

A mechanical testing apparatus for a specimen, the mechanical testing apparatus comprising:
a drop table system having a drop carriage; and
a Hopkinson bar positioned parallel to a motion of the drop carriage and connected to the drop table system by the specimen;
wherein the drop table system comprises:
an impact plate having a threaded hole configured to hold a first end of the specimen, wherein the drop carriage is configured to move towards the impact plate;
an impactor connected to the drop carriage, the impactor configured to strike a pulse shaper associated with the impact plate;
an accelerometer connected to the impact plate;
a plurality of guide rods extending through the impact plate;
a plurality of springs surrounding each of the plurality of guide rods;
a bottom plate connected to the plurality of guide rods; and
a bumper connected to the bottom plate, wherein the bumper is configured to absorb momentum and stop the impact plate.

### Claim 2 (depends on 1)

The mechanical testing apparatus of claim 1, wherein the mechanical testing apparatus is configured to obtain a tensile stress-strain response of the specimen at intermediate strain rates in the order of 102 s−1.

### Claim 3 (depends on 2)

The mechanical testing apparatus of claim 2, wherein the mechanical testing apparatus is further configured to obtain a tensile stress-strain response at higher or lower strain rates by varying an impact speed of the drop carriage of the drop table system.

### Claim 4 (depends on 1)

The mechanical testing apparatus of claim 1, wherein the specimen has a threaded engagement with each of the drop table system and the Hopkinson bar.

### Claim 5 (depends on 1)

The mechanical testing apparatus of claim 1, wherein a strain of the specimen is calculated as
ɛ
⁡
(
t
)
=
∫
0
t
⁢
ɛ
.
⁢
⁢
dt
=
∫
0
t
⁢
∫
0
t
⁢
a
⁡
(
t
)
⁢
⁢
dt
-
C
0
⁢
ɛ
0
⁡
(
t
)
L
s
⁢
⁢
dt
wherein a(t) is an acceleration history recorded by the accelerometer; C0 is a speed of an elastic stress wave in a material of the Hopkinson bar; wherein
C
0
=
E
0
ρ
0
;
wherein ρ0 is a density of the material of the Hopkinson bar; and Ls is a gauge length of the specimen.

### Claim 6 (depends on 1)

The mechanical testing apparatus of claim 1, wherein the Hopkinson bar comprises a metal bar and a number of strain gauges connected to a surface of the metal bar.

### Claim 7 (depends on 6)

The mechanical testing apparatus of claim 6, wherein specimen stress is calculated as
σ
⁡
(
t
)
=
A
0
A
S
⁢
E
0
⁢
ɛ
0
⁡
(
t
)
,
wherein A0 is a cross-sectional area of the Hopkinson bar, wherein As is a cross-sectional area of the specimen, E0 is a Young's modulus of the Hopkinson bar, and ε0 is a bar strain recorded with the number of strain gauges.

### Claim 8 (depends on 6)

The mechanical testing apparatus of claim 6, wherein the metal bar is suspended by a spring attached to a first end of the metal bar.

### Claim 9

A mechanical testing apparatus for a specimen, the mechanical testing apparatus comprising:
a drop table system having a drop carriage; and
a Hopkinson bar positioned parallel to a motion of the drop carriage and connected to the drop table system by the specimen;
wherein the drop table system comprises:
an impact plate configured to hold the specimen;
a plurality of guide rods extending through the impact plate;
a plurality of springs surrounding each of the plurality of guide rods;
a bottom plate connected to the plurality of guide rods; and
a bumper connected to the bottom plate, wherein the bumper is configured to absorb momentum and stop the impact plate.

### Claim 10 (depends on 9)

The mechanical testing apparatus of claim 9, comprising an accelerometer connected to the impact plate.

### Claim 11 (depends on 9)

The mechanical testing apparatus of claim 9, wherein the specimen is threadably engaged with each of the drop table system and the Hopkinson bar.

### Claim 12 (depends on 9)

The mechanical testing apparatus of claim 9, wherein the mechanical testing apparatus is configured to obtain a tensile stress-strain response of the specimen at intermediate strain rates in the order of 102 s−1.

### Claim 13 (depends on 12)

The mechanical testing apparatus of claim 12, wherein the mechanical testing apparatus is further configured to obtain a tensile stress-strain response at higher or lower strain rates by varying an impact speed of the drop carriage.