Investigation of additive manufactured micro-lattice structures for defence applications

Shaik, Ameer Malik; Reddy, Bobbili Veera Siva; Sastry, C. Chandrasekhara; Krishnaiah, J.; Ramakrishna, B.

doi:10.2478/msp-2023-0023

Figures & Tables

Micro-lattice structure design: (a) honeycomb and (b) gyroid

(a) Laser powder bed fusion process for printing of micro-lattice specimens: EOS M290; (b) micro-lattice specimens honeycomb and gyroid; (c) w-EDM machine; (d) Micro Vickers hardness machine; (e) surface roughness measurement device

Coupon preparation for morphological tests

LPBF A286 powder: (a) EDS analysis, (b) elemental distribution and (c, d) SEM images of A286 powder

OM and SEM images for (a-d) RHA (e-h) MHA (i-l) HNS

OM and SEM images for honeycomb lattice structures: (a–d) as printed; (e–h) stress relieved; (i–l) heat treated

OM and SEM images for gyroid lattice structures: (–d) as printed. (e–h) stress relieved, (i–l) heat treated

Micro-lattice A286 test specimens placed in salt spray test chamber

X-ray diffraction plot (a) RHA, MHA, HNS; (b) honeycomb and gyroid micro-lattice structures

Response variables, surface roughness, and micro-Vickers hardness for the honeycomb micro-lattice structure

Non-stress relived (as printed)
				Surface roughness (Ra)			Micro-Vickers Hardness (HV)
S.No.	Lattice	Design	Non-stress relieved	Average (Ra)	Max	Min	Average	Max	Min
1	Honeycomb	Design 1	2A	11.29	11.64	10.54	219HV1	225	213
2	Honeycomb	Design 2	3A	9.94	11.84	9.36	220HV1	227	215
3	Honeycomb	Design 3	4A	11.18	11.18	9.87	230HV1	242	218
4	Honeycomb	Design 4	5A	8.91	12.6	8.54	213HV1	218	207
5	Honeycomb	Design 5	6A	11.69	12.34	9.03	194HV1	201	190
Stress relieved
S.No.	Lattice	Design	Stress relieved	Average (Ra)	Max	Min	Average	Max	Min
1	Honeycomb	Design 1	2B	14.58	24.26	9.23	233HV1	239	228
2	Honeycomb	Design 2	3B	14.79	17.12	10.48	214HV1	220	209
3	Honeycomb	Design 3	4B	13.76	15.91	12.11	193HV1	197	190
4	Honeycomb	Design 4	5B	12.26	13.66	11.43	222HV1	226	218
5	Honeycomb	Design 5	6B	20.24	24.23	17.19	220HV1	226	216
Heat treated (Final specimens)
S. No.	Lattice	Design	Heat treated	Average (Ra)	Max	Min	Average	Max	Min
1	Honeycomb	Design 1	2C,2D,2E	11.59	15.2	9.12	460HV1	475	451
2	Honeycomb	Design 2	3C,3D.3E	7.77	7.94	7.65	418HV1	425	412
3	Honeycomb	Design 3	4C,4D,4E	7.67	8.46	6.63	423HV1	426	420
4	Honeycomb	Design 4	5C,5D,5E	8.82	8.87	8.77	460HV1	470	451
5	Honeycomb	Design 5	6C.6D,6E	11.92	12.81	10.41	455HV1	461	450

Response variables, surface roughness, and micro-Vickers hardness for the gyroid micro-lattice structure

Non-stress relived (as printed)
				Surface roughness (Ra)			Micro-Vickers hardness (HV)
S. No.	Lattice	Design	Non-Stress Relieved	Average (Ra)	Max	Min	Average	Max	Min
1	Gyroid	Design 1	1A	10.5	12.86	8.11	215HV1	220	211
Stress relieved
S. No.	Lattice	Design	Stress relieved	Average (Ra)	Max	Min	Average	Max	Min
1	Gyroid	Design 1	1B	11.85	13.46	10.83	226HV1	229	222
Heat treated (final specimens)
S. No.	Lattice	Design	Heat treated	Average (Ra)	Max	Min	Average	Max	Min
1	Gyroid	Design 1	1C,1D,1E	3.56	3.74	3.37	418HV1	425	411

Particle size distribution – sieve analysis

Particle size (μm)	Sieve number	% by mass
<45	−325	78.28
>45	+325	17.28
>53	+270	3.78
>63	+230	0.65

Corrosion rate for RHA, MHA, HNS, honeycomb, and gyroid micro-lattice structures

Case	Specimen	Initial weight (g)	Final weight (g)	Total weight loss (g)	Corrosion rate (mm/ year)
Existing materials	RHA	12.4093	12.4029	0.0064	2.847817577
	MHA	11.8837	11.8795	0.0042	1.868880285
	HNS	13.6118	13.6066	0.0052	2.313851781
Honeycomb lattice	5D (ideal)	77.6933	77.3803	0.313	1.218227858
structure	6D (non-ideal)	80.6307	80.3128	0.3179	1.237299156
Gyroid	1D	40.0436	39.9027	0.1409	1.671511872

Flow rate, apparent, and tap density test results

Test	Test method	Results
Flow rate	ASTM B213	18s/50g
Apparent density	ASTM B212	3.98g/cm³
Tap density	ASTM B527	4.65g/cm³

Compressive residual stress for RHA, MHA, HNS, honeycomb and gyroid micro-lattice structures

Material	Compressive residual stress values (MPa)
Existing Materials
RHA	306.627
MHA	348.454
HNS	432.367
Micro-metallic lattice structures
Honeycomb	581.907
Gyroid	483.679

Corrosion resistance (in %) of micro-metallic lattice structures: honeycomb and gyroid vs_ RHA, MHA, and HNS

Before compression
Comparison of corrosion rate	Percentage difference	Comparison of corrosion rate	Percentage difference
Honeycomb vs. RHA	57.23%	Gyroid vs. RHA	41.31%
Honeycomb vs. MHA	34.83%	Gyroid vs. MHA	10.6%
Honeycomb vs. HNS	47.36 %	Gyroid vs. HNS	27.75%
After compression tests
Honeycomb vs. RHA	37.61%	Gyroid vs. RHA	17.88%
Honeycomb vs. MHA	4.92%	Gyroid vs. MHA	25.16%
Honeycomb vs. HNS	23.21%	Gyroid vs. HNS	1.08%
Micro-metallic lattice structures
Honeycomb vs. gyroid (before compression)		27.11%
Honeycomb vs. gyroid (after compression)		24.03%

Micro-lattice structure design variations

Gyroid	Design 1
Dimensions (L × W × H) (mm) 24 × 20 × 30
Honeycomb	Design 1	Design 2	Design 3	Design 4	Design 5
Dimensions (L × W × H) (mm)	24 × 20 × 30
Wall thickness (mm)	2	2	2	2	2
Detail size (mm)	1	1	1	1	1
Hole diameter (mm)	1.4	1.2	1	0.8	0.5
Infill thickness (mm)	1.4	1.2	1	0.8	0.5

Corrosion rate for honeycomb and gyroid micro-lattice structures after compression test

Case	Specimen	Initial weight (g)	Final weight (g)	Total weight loss (g)	Corrosion rate (mm/year)
Honeycomb lattice	5C (ideal)	82.129	81.6725	0.4565	1.776744463
structure	6C (non-ideal)	78.4252	77.9683	0.4569	1.778301304
Gyroid	1C	32.1465	31.9494	0.1971	2.338218523

Compressive residual stress comparison of micro metallic lattice structures honeycomb and gyroid vs_ RHA, MHA, and HNS

Comparison of residual stress values	% Increase in residual stress	Comparison of residual stress values	% Increase in residual stress
Honeycomb vs. RHA	47.30%	Gyroid vs. RHA	36.6%
Honeycomb vs. MHA	40.12%	Gyroid vs. MHA	27.96%
Honeycomb vs. HNS	25.70%	Gyroid vs. HNS	10.61%
Micro-metallic lattice structures
Honeycomb vs. Gyroid		16.88%

TOPSIS analysis for honeycomb micro-lattice structure for LPBF-generated specimens

Non-stress-relieved condition
Normalized residual matrix			Weighted residual matrix		Distance to ideal
Coupon no.	NRa	NVHN	WRa	WVHN	Si+	Si-	Ci	Rank
2A	0.369	0.419	0.185	0.209	0.039	0.007	0.154	4
3A	0.325	0.421	0.163	0.210	0.017	0.029	0.633	2
4A	0.365	0.440	0.183	0.220	0.037	0.010	0.204	3
5A	0.291	0.408	0.146	0.204	0.000	0.046	0.994	1
6A	0.382	0.371	0.191	0.186	0.047	0.001	0.002	5
Stress-relieved condition
Normalized residual matrix			Weighted residual matrix		Distance to ideal
Coupon no.	NRa	NVHN	WRa	WVHN	Si+	Si-	Ci	Rank
2B	0.477	0.446	0.239	0.223	0.038	0.094	0.713	3
3B	0.484	0.409	0.242	0.205	0.042	0.090	0.682	4
4B	0.450	0.369	0.225	0.185	0.026	0.106	0.803	2
5B	0.401	0.425	0.201	0.212	0.000	0.131	0.999	1
6B	0.662	0.421	0.331	0.210	0.131	0.001	0.005	5
Heat-treated condition
Normalized residual matrix			Weighted residual matrix		Distance to ideal
Coupon no.	NRa	NVHN	WRa	WVHN	Si+	Si-	Ci	Rank
2C,2D,2E	0.379	0.880	0.190	0.440	0.064	0.007	0.099	4
3C,3D.3E	0.254	0.800	0.127	0.400	0.003	0.068	0.954	2
4C,4D,4E	0.251	0.809	0.125	0.405	0.001	0.070	0.982	1
5C,5D,5E	0.289	0.880	0.144	0.440	0.019	0.052	0.736	3
6C.6D,6E	0.390	0.871	0.195	0.435	0.070	0.001	0.018	5

Physical properties of A286 steel

Property								Value
Ultimate tensile strength								620 MPa
Yield strength								275 MPa
Elongation at break								40%
Modulus of elasticity								201 GPa
Poisson’s ratio								0.3
Shear modulus								77 GPa
Reduction of area								20%
Chemical composition (% weight factor) of A286 steel
Element	C	Mn	Si	P	S	Ni	Cr	Mo	V	Al	Ti	Cu	Fe
Weight (%)	0.034	0.126	0.236	0.012	0.006	25.62	15.40	1.331	0.196	0.209	2.054	0.014	Bal.

Investigation of additive manufactured micro-lattice structures for defence applications

Figures & Tables

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Response variables, surface roughness, and micro-Vickers hardness for the honeycomb micro-lattice structure

Response variables, surface roughness, and micro-Vickers hardness for the gyroid micro-lattice structure

Particle size distribution – sieve analysis

Corrosion rate for RHA, MHA, HNS, honeycomb, and gyroid micro-lattice structures

Flow rate, apparent, and tap density test results

Compressive residual stress for RHA, MHA, HNS, honeycomb and gyroid micro-lattice structures

Corrosion resistance (in %) of micro-metallic lattice structures: honeycomb and gyroid vs_ RHA, MHA, and HNS

Micro-lattice structure design variations

Corrosion rate for honeycomb and gyroid micro-lattice structures after compression test

Compressive residual stress comparison of micro metallic lattice structures honeycomb and gyroid vs_ RHA, MHA, and HNS

TOPSIS analysis for honeycomb micro-lattice structure for LPBF-generated specimens

Physical properties of A286 steel

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