Design Optimization of Connector Secondary Latch to Avoid Failure in Automotive Connectors

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 10 Issue: 11 | Nov 2023 www.irjet.net p-ISSN: 2395-0072
© 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 781
Design Optimization of Connector Secondary Latch to Avoid Failure in
Automotive Connectors
1*Jagadeesh Patil, 2J Sharana Basavaraja
1Mechanical Department, B.M.S College of Engineering, Bengaluru, India.
2Mechanical Department, B.M.S College of Engineering, Bengaluru, India.
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Abstract - Automotive connectors are essential elements in modern automobiles, ensuring reliable and secure electrical
connections for a variety of systems. Among these connectors, miniature connectors with hinged latches play a crucial role in
maintaining electrical continuity. The hinge failures and cracks that can appear on these connectors at the hinged junction,
however, may affect their function and raise safety issues. This paper presents a comprehensive design optimizationapproach for
the independent secondary lock (ISL) mechanism in automotive connectors. The primary objectives are to minimize von Mises
stress and logarithmic strain, which will ultimately reduce the risk that cracks would occur and the hinge will collapse.
The study involves a comprehensive evaluation of various hinge profiles while keeping material, and operational aspects into
unchanged. The mechanical behavior of various hinge configurations is assessedusingrefinedFEAmodelsunderaccurateloading
conditions. The results show that particular hinge profiles exhibit improved stress distribution and strain reduction, significantly
reducing the occurrence of crack marks at the hinged joint. Additionally, to ensurethemodifiedhingeprofile's improvedefficiency
in decreasing crack marks, The findings show that cracks has significantly decreased, improving the connections' long-term
dependability and durability.
Key Words: Crack Marks, FEA analysis, Hinge profile design, Miniature connector, Design Optimization.
1.INTRODUCTION
Snap fit system requires a lot of effort to design and integrate to improve the functionality and producibility of these critical
joints. The focus in snap-fit application has traditionally been on precisely engineering individual features, accounting for
elements such as deformable beam diameters and unique locking mechanisms suited to various snap-fit kinds and cross-
sectional area. Recent developments, however,havehighlightedthesignificanceofa holisticdesignperspectivethatseamlessly
integrates both the conceptual and detailed design stages. The dimensions of the deflection mechanisms are determined, and
retention elements are incorporated into the lockingsystem,simultaneouslyduringthedetaileddesignphases.Drawingonthe
wide body of literature on general snap-fit designs, especially for cantilever snap fit joints, is often needed for this.
An independent secondary lock (ISL) is a type of locking mechanism to ensure a secure and reliable connection between two
components. It is called “independent” because it is separate from the primary locking mechanism and provides an additional
layer of security. We can see whitening markings at the hinge region of this specific connector when ISL closes as it advances
from the pre-lock to final lock positions.
2.0 MATERIALS AND METHODOLOGY
2.1 MATERIALS:
The research work involves usage of miniature Connector which are made up of a special type of Polymer named PBT fiber
glass reinforced 6% (Polybutylene terephthalate), which has an excellent balanceofmechanical propertiesandprocessability.
It possesses high strength, better dimensional stability and low creep properties. PBT is noteasytodecomposeunderwaterat
normal temperature. Also, it has excellent insulation properties which makes it ideal material for electrical and electronics
parts. And due to fast crystallization speed and better fluidity the mold temperature of PBT is lowerthanthe mostengineering
plastics.

2.2 METHODOLOGY:
3.0 MATERIAL PROPERTIES
Description Type/ value
Material PA66 (Nylon)
Nominal elongation 4%
Density in Kg/m3 1.36E-9
Poisson’s ratio 0.35
Yield strength in M Pa 59 M Pa
4.0 MESHING
To improve simulation accuracy, the connector housing and latch were meshed using second-ordertetrahedral elements.The
mesh was improved in critical areas such contact areas, stress concentration areas, and areas of relevance to maximize
computational efficiency.
A 2D fine meshing was used when meshing the latch component, resulting in a denser grid of mesh elements with an element
size of 0.1mm. This method focused on specific geometry areas that neededcloser examination,likethestressconcentrationat
the hinge region and the contact surface of the latch. This approach represents local behaviors and stress changes more
accurately than a homogeneous mesh because it distributes computing resources to where they are most needed. The
geometry's complexity, as well as the expected stressdistributionandstrainrelaxation,provideasa guidanceinchoosingthese
particular regions. The simulation can better capture intricate behaviors that would be missed with a coarser mesh, which is
set at 0.8mm in other locations, by using a finer mesh in certain areas.

Fig 1: Connector latch Meshing
To replicate real world conditions, the mentioned nodes of the connector’s housing are fixed as shown in above figure. This
simulates the testing procedure, and how the housing is securely held. The top surface nodes of the latch component are fixed
in Z direction as shown above to represent the constraints during operation
Fig. 2: 2D latch Meshing.
A service tool or rigid plate is used to provide force during the connector assembly procedure in a realistic testing setting.
This plate is subjected to displacement in the Y-direction in order to replicate the latch component contacting with the
connector housing. The latch is given a displacement of 2.5 mm from its pre-lock position to its final lock position in this
instance.
In this analysis, a contact friction coefficient of 0.1 is introduced to accountforinteractionsbetweenhousingandthelatch. This
methodical approach is anticipated to significantly reduce the computational overheads associated with pre-processing and
post-processing within the software, enhancing efficiency and overall optimization of the automobile connector assembly
design in terms of efficient ISL engaging process.
5.0 SIMULATION STUDY FOR EXISTING DESIGN
FEA simulations are done by keeping the same material and only focusing on the different latch profiles in the analysis. In the
first iteration, the simulation is done using 3D model Fig 3 shows the logarithmic strain distribution and Von-mises stress
distribution in the connector. As the latch approaches the final lock position maximum logarithmic strain was observed at the
hinge region which leads to crack marks in the hinge region.

Fig. 3: 3D latch stress and strain overview.
To reduce the computational time, 2D section was considered for the simulation. Fig 4.1 shows 2D latch design. where
reduction in the width of latch’s slant edge is very less which further indicates that hingeregiondoesn’thavesufficientarea for
the stress distribution and hence causing higher stress values in the hinge region.
6.0 OPTIMIZED DESIGN OF THE CONNECTOR LATCH
One of the design constraints was to use the same material and focusing only on the different latch profiles in the analysis. All
the required dimensional changes were made using NX Siemens software. Notably, the latches were designed in such a way
that, this alteration aimed to optimize and eliminate crack marks that formed on the hinge region resultinginwhiteningmarks
on the hinge region in Connector. By proposing new latch profiles at the hinge region design was optimized and results aimed
to have better stress relaxation and decreased logarithmic strain values. Furthermore, the latch engaging forcewasmeasured
when it reaches final lock position in the housing, and it made sure thislatch engagingforcevaluesmeettheacceptancecriteria
as per the United States council of automotives research standard.
7.0 D OPTIMIZED LATCH DESIGNS:
As baseline design has less reduction in the width of latch’s slant edge, in option 2 it was optimized and made sure that
specified dimension at the hinge region is sufficient forthestress to distributeat the hinge region. In further designsinoption3
profile of hinge is made more likely circular in this design with proper blend radius making the latch deforming within limit.
Which makes option 3 design better compared to all other designs and expecting more reduced logarithmic strain values and
better stress relaxation in the hinge region. Option 4 design has different profile at the hinge region compared to all other
previous latch designs, expecting a better stress relaxation with much reduced logarithmic strain values at hinge region.
Fig a: (Option 1) Fig b: (Option 2)

Fig c: (Option 3) Fig d: (Option 4)
Fig 4: 2D latch design.
8.0 OPTIMIZED DESIGN RESULTS:
The initial design of the connector latch was havingcrack marks at the hingeregion aslatchmovesfromitspre-lockposition
to final lock position. Analysis resultsshows that when latch reaches its final lock position boththestressandlogarithmicstrain
values crosses the critical values of the material. And it is found that these exceeded logarithmic strain values are causing crack
marks at the hinge region. Hence the study with different latch profile designs were considered and finally found that Option 3
was better among all the optimized designs as it significantly reduces the logarithmic strain values at the hinge region and
eliminating the risk of having crack marks.
Fig a: 2D latch design (Option 1) results.
Fig b: 2D latch design (Option 2) results.

Fig c: 2D latch design (Option 3) results.
Fig d: 2D latch design (Option 4) results.
9.0 TESTING & CORRELATION
Consider 10 connectors and do inspection with the naked eyes for pretest inspection. secure the connector housing in an
appropriate fixture. Using appropriate push rod, push the latch from pre-lock to final lock at a uniform rate of 50 mm/min.
Record the maximum force. The Fig below shows the force testing equipment with the connector is held.
Figure 6: Force testing equipment
Component - loose piece latch, engage force was done to validate the accuracy and reliability of the simulation results by
comparing them to real word data. Box plots were plotted usingMinitabsoftwaretoknowthespreadofthedata andtoidentify
the outliers due to any unavoidable circumstance.

Fig 7: Boxplots & Capability plots for ISL engage force values
The results of the test verified that the component - loose piece latch, engage force test results met the acceptance criteria of
USCAR standards for which we were validating theconnector.Andprocesscapability sixpack reportshows thatPPMvaluesare
equals to zero. Which indicates that there are zero failure parts per million.
10.0 CONCLUSION
 The investigation resulted in a better latch profile design that exhibited a noticeable reduction in the logarithmic strain
value as the latch approached its final lock position.
 The decreased logarithmic strain value that was seen in the simulated testing is evidence that the design optimization
efforts were successful. The modified design enhanced the integrity of the latch contact in addition to reducing the strain
values. This is necessary to maintain consistent and reliable electrical connections and to keep the terminals in their
proper locations in many automotive systems, which enhances the performance and safety of the vehicle.
 The study highlighted the importance of approaching automotive engineering from various disciplinary angles. The
collaboration of mechanical design, material science, and electrical engineering resultedtoa comprehensiveandeffective
design solution.
 The accuracy and usefulness of the simulation tools were proven through the validation process, which comprised
comparing simulation results to actual measurements. This validated both the design optimization and the validity of the
simulation methodologies.
11.0 LIMITATIONS AND COST IMPLIPICATIONS
 These connectors with improvised ISL design can be used in the applications where only 10 engage- disengage cycles of
ISL are limited.
 These new ISL design may pose challenges for manufacturing team to mold it from 2-piece injection molding process.
 New mold inserts have to be used to produce the connectors with the optimized ISL design. Meanwhilethesameinjection
molding setup can accommodate these design changes, the cost of production should be less in long term production.
12.0 REFERENCES
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Design Optimization of Connector Secondary Latch to Avoid Failure in Automotive Connectors