Abstract

Machine guards provide protection against the ejection of parts during operation, such as chips or workpiece fragments. They are considered safe if the impact resistance is at least as high as the resulting projectile energy in the worst case of damage. To protect the machine operator, the impact resistance of machine guards is determined according to ISO standards. The bisection method can be used to determine the impact resistance through impact tests. However, this method is inaccurate for a small number of impact tests and does not indicate uncertainties in the determination. Moreover, the result of testing is validated in different ways depending on the standard utilized for testing. Relevant uncertainties affecting impact testing and a new probabilistic approach for assessing the impact resistance using the Recht and Ipson equation are presented. With multiple impact tests at different initial velocities a Recht and Ipson best-fit curve and a confidence interval for a ballistic limit can be obtained, which is used to determine the impact resistance by defining a velocity reduction coefficient. This method can be applied to any machine guard made of ductile material. This paper validates the Recht and Ipson method by performing impact tests with a standardized 2.5 kg projectile on polycarbonate sheets of different thicknesses. Determination of the ballistic limit showed good agreement with experimental results. With the ballistic limits, the velocity reduction coefficients have been found to determine the impact resistances. Therefore, an alternative method for standardized tests to determine the impact resistance was found.

References

1.
ISO 14120, 2015, “Safety of Machinery Guards: General Requirements for the Design and Construction of Fixed and Movable Guards,” ISO International Organization for Standardization, Geneva, Switzerland.
2.
ISO 16090-1, 2018, Machine Tools Safety – Machining Centres, Milling Machines, Transfer Machines – Part 1: Safety Requirements, ISO International Organization for Standardization, Geneva, Switzerland.
3.
ISO 19085-1, 2017, Woodworking Machines – Part 1: Common Requirements, ISO International Organization for Standardization, Geneva, Switzerland.
4.
Landi
,
L.
,
Moedden
,
H.
,
Pera
,
F.
,
Uhlman
,
E.
, and
Meister
,
F.
,
2017a
, “
Probabilities in Safety of Machinery-Risk Reduction Through Fixed and Movable Guards by Standardized Impact Test. Part 1: Applications and Consideration of Random Effects
,” The 2nd International Conference on Engineering Sciences and Technologies,
ESREL, pp. 1013-LL-rev2.10.1201/9781315210469-272
5.
Landi
,
L.
,
Moedden
,
H.
,
Pera
,
F.
,
Uhlman
,
E.
, and
Meister
,
F.
,
2017b
, “
Probabilities in Safety of Machinery-Risk Reduction Through Fixed and Movable Guards by Standardized Impact Test. Part 2: Possible Improvements With FE Impact Simulations
,” The 2nd International Conference on Engineering Sciences and Technologies,
ESREL, p.
995
.10.1201/9781315210469-246
6.
Børvik
,
T.
,
Langseth
,
M.
,
Hopperstad
,
O. S.
, and
Malo
,
K. A.
,
2002
, “
Perforation of 12 mm Thick Steel Plates by 20 mm Diameter Projectile With Flat, Hemispherical and Conical Noses. Part 1: Experimental Study
,”
Int. J. Impact Eng.
,
27
(
1
), pp.
19
35
.10.1016/S0734-743X(01)00034-3
7.
Børvik
,
T.
,
Hopperstad
,
O. S.
,
Berstad
,
T.
, and
Langseth
,
M.
,
2002
, “
Perforation of 12 mm Thick Steel Plates by 20 mm Diameter Projectile With Flat, Hemispherical and Conical Noses. Part 2: Numerical Simulations
,”
Int. J. Impact Eng.
,
27
(
1
), pp.
37
64
.10.1016/S0734-743X(01)00035-5
8.
Landi
,
L.
,
Stecconi
,
A.
,
Pera
,
F.
,
Del Prete
,
F.
, and
Ratti
,
C.
,
2019
, “
Influence of the Penetrator Shape on Safety Evaluation of Machine Tools Guards
,” Proceedings of the 29th European Safety and Reliability Conference (
ESREL
), Hannover, Germany, Sept. 22–26, pp. 2936–2943. 10.3850/978-981-11-2724-3_0296-cd
9.
Uhlmann
,
E.
,
Haberbosch
,
K.
,
Thom
,
S.
,
Drieux
,
S.
,
Schwarze
,
A.
, and
Polte
,
M.
,
2019
, “
Investigation on the Effect of Novel Cuting Fluids With Modified Ingredients Regarding the Long-Term Resistance of Polycarbonate Used as Machine Guards in Cutting Operations
,”
Proceedings of the 29th European Safety and Reliability Conference (ESREL)
, Hannover, Germany, Sept. 22–26, pp.
2944
2953
.
10.
Uhlmann
,
E.
, and
Duchstein
,
B.
,
2010
, “
Aufprallprüfungen an Definiert Gealterten Polycarbonat Sichtscheiben
,”
Futur Vision Innovation Realisierung
, Futur 01/2010.
11.
Bold
,
J.
,
2004
,
Trennende Schutzeinrichtungen Für Werkzeugmaschinen Zur Hochgeschwindigkeitsbearbeitung (Separating Protective Devices for Machine Tools for High-Speed Machining), Stuttgart: Fraunhofer IRB Verlag, p. 201.
12.
Recht
,
R. F.
, and
Ipson
,
T. W.
,
1963
, “
Ballistic Perforation Dynamics
,”
ASME J. Appl. Mech.
,
30
(
3
), pp.
384
390
.10.1115/1.3636566
13.
Landi
,
L.
, and
Amici
,
D.
,
2016
, “
Steel Sheets Impact Simulation for Safety Guards Design: Problems and Pespectives
,”
ASME
Paper No. IMECE 2016-65181.10.1115/IMECE2016-65181
14.
Stecconi
,
A.
, and
Landi
,
L.
,
2020
, “
Finite Element Analysis for Impact Tests on Polycarbonate Safety Guards: Comparison With Experimental Data and Statistical Dispersion of Ballistic Limit
,”
ASCE-ASME J. Risk Uncertainty Eng. Syst., Part B
,
6
(
4
), p.
041004
.10.1115/1.4047464
15.
Landi
,
L.
,
Stecconi
,
A.
,
Pera
,
F.
, and
Prete
,
E. D.
,
2020
, “
Calibration of an Air Cannon for Safety Penetration Tests
,”
Proceedings of the 30th European Safety and Reliability Conference and the 15th Probabilistic Safety Assessment and Management Conference
, Venice, Italy, Nov. 1–5, pp.
3967
3973
.10.3850/978-981-14-8593-0_4893-cd
16.
Mewes
,
D.
, and
Trapp
,
R. P.
,
2000
, “
Impact Resistance of Material Guards on Cutting Machine Tools – Requirements in Future European Safety Standards
,”
Int. J. Occup. Saf. Ergon.
,
6
(
4
), pp.
507
520
.10.1080/10803548.2000.11076469
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